GF disclosed previous BF was well-endowed, was with him just for the sex, ranked me bottom half. I freaked out, now GF has no libido. Help!

My girlfriend and I have been together now for two years. It has been a tumultuous relationship at times (we both came with a lot of baggage), but overall it's been the most successful relationship either of us has had. I should stress at the outset that all of our stresses revolve around our sex life. Aside from sex, our relationship is actually pretty awesome, and we get along very well. Which makes all this worse.....

Our sex life has always been disappointing, divisive, and extremely problematic. Prior to my current girlfriend, I'd had intercourse with only one other person; I had lost my virginity close to 27. This was not deliberate. I very much wanted to have sex (though I think that was largely a function of my loneliness).

Anyway, I wasn't with my first partner very long, but she frequently complained that our sex was "boring and lame." Worse, prior to her, pretty much everyone who had ever seen my penis commented on how small it was, including girls I'd dated. (Nothing stings so much as a girl sneering, "You've got a tiny dick.") For the record, it's about 1.5-2" flaccid and about 4.25-4.75" hard. Fully erect it's at least 5" even, but even though I'm in my 20's, I suffer from fairly severe erectile dysfunction, and the Viagra can only do so much.

Anyway, after my first sexual partner broke up with me, I resolved to get over her by acting as fratty and bro-ish as possible -- I succeeded. So, when my current girlfriend and I first started hooking up, she expected me to thoroughly dominate her: she constantly baited me (goodnaturedly but seriously) to "show me what you've got." She was in fact insecure about herself because she believed that someone as fratty, hard-drinking, and hard-partying as me would surely have bedded at least 15-20 women.

Anyway, the truth eventually came out. My previous girlfriend's comments that sex with me was boring and lame fucked with my head -- I was obviously nonconfident and admitted I had only been with one other person. This, by itself, may not have been so bad. Unfortunately, my current girlfriend lacked discretion and mentioned her previous partners casually. She mentioned several times one gent in particular, let's call him "A", who she told me was well-endowed, that she had dated only because he was good in bed, and that his size was part (or all) of the reason for his talent in bed. She also decided to mention that he was so big he would hit her cervix and hurt her. She also had informed me sometime around our second date "don't kid yourself, [boyfriend]... size matters." She also disclosed that one of her partners had once came, stayed inside of her, then got hard again, leading to another round of sex. (When she told me this she was positively beaming, even though I was literally on top of her, immediately post-coitus). And we were once in a parking garage trying to find a parking space when she eagerly started telling me/wondering aloud whether this was where she had had sex one time. (I feel like I've heard something about her sex life with all of her partners and ex's now). Also, after we had been having trouble in bed for a while (and because I was so insecure), I once asked her how good the sex was and she ranked me in the bottom half of her lovers (but said near the middle to make me feel better). Importantly, she confessed that she loved sex and liked having it often. Lastly, when we first started having sex, she would constantly say, "deeper... deeper!" even though I was as deep as I could go. That disappeared after the first month or two.

Anyway, I developed quite a complex about this situation. For years I had harbored a nightmare scenario wherein I would fall in love with some girl who had previously dated a well-endowed, sexually superior man -- and here my fear had become my reality. Because of my insecurity, my normal erection difficulties were exponentially greater: even with a maximum dose of Viagra, I couldn't get hard. Moreover, Viagra requires a good 45 minutes of lead time, and it's only effective for several hours afterward. So, basically, spontaneous sex was out of the question. After a few months of dating, my girlfriend had had it and every time we tried to be intimate, it ended with her more frustrated and bitter than almost any woman I've seen -- she would wail that sex had never been worse for her, that she hated it now, that all the fun had been eliminated, that it was a chore and an obligation, and that she couldn't believe how unenjoyable it all was. We had sex infrequently.

(I have no idea whether it provides useful context, but after we'd been dating for four months she had to undergo a procedure to remove precancerous cells from her cervix. She had contracted HPV... almost certainly from "A," her previous, well-endowed partner).

This, as you might imagine, did not do much to help my confidence. All that was about a year ago. For the last year, our sex life has improved somewhat (to the point where we don't really fight about it), but she almost always rebuffs my advances (even she'll admit it's probably around 80-90%). In retrospect, I have no idea how we've survived. Anyway, my confidence has gradually improved.

So this is where things now stand (greatly abbreviated because this post is getting so long): My girlfriend says she enjoys the sex we have, once we're actually having it. However, she says she's incapable of becoming aroused or wet without me first going down on her, and even then she tends to be pretty dry until we've been going at it for a minute or two. She says this is because she can't help but automatically fear that I have an expectation of sex and that it's her duty to have sex with me. (This was true in the past, but I long since stopped caring, and I'm ashamed I ever thought that in the first place). In general, though, she has zero libido and I feel like having sex with me has destroyed her sexuality.

Admittedly, she wants me to be more confident and says that'll help things in bed. Yes, I know confidence counts for a huge amount. On the other hand, she's admitted that she would probably rebuff my advances no matter what I did, because she's so conditioned now to doing so. I personally think my confidence is pretty okay (that is, I think my sexual talents are better than adequate), but besides all of the other difficulties here... I still am paranoid about her well-endowed partner, as well as her boyfriend immediately before me (she has suggested that he was also above-average, although not so much as the other guy). Specifically, I don't see how I could ever be anywhere near the top of her ranking, given what seems to be the importance of size. She swears that "speaking as woman, [she] has absolutely no problem" with the size of my penis, but I feel like her disclosures about her ex's suggest otherwise. That, and she's only capable of orgasming through penetrative sex.

Anyway, at this point I feel resigned. I just want to have sex at least occasionally. I realize our relationship must sound absurdly dysfunctional -- but we've been together two years and still have great conversations. I don't want to lose that. It has also been a long time (8-9 months at least) since she said anything, well, like what she said before -- the miracle of therapy. Lastly, she has really been there for me in X number of ways: as awful as things have been, she's also been incredibly loyal and extremely supportive of everything outside of bed.

I don't know what to do. Any thoughts whatsoever would be welcomed. If you read through all this... well, that's some shit, my friend. Thank you for listening.

TL;DR My girlfriend told me about her previous sexual experiences and well-endowed partner(s), for months complained how terrible sex with me was, and I've got a somewhat below-average sized dick that works only sporadically.