23M 23F extremely unsure about my confidence in our sex life after 4 years, do I have unrealistic expectations?

My girlfriend and I have been together for 4 years and known each other for 5. Things started out fun and playful when we were both new to each other.

After about a year she slowly moved herself in by staying one night and then another and so on and on at my parents house. That was sort of alright with me although I struggled with the move in period quite a bit internally since it was never a discussion and we later went on to move into an apartment (we both decided that one).

Even at the start I always felt a craving for more sexually but I just pushed it to the back of my head thinking that I’m a high libido sex crazed monkey but I do feel like that disparity is catching up to me after a long time. She isn’t very adventurous at all ( I would try quite literally everything and anything once for fun), extremely vanilla to the point where I’ve asked multiple times what she’s into or what she likes in order to spice things up to which she couldn’t answer.

\\\\\\\\\\\\\\\*\\\\\\\\\\\\\\\*It honestly feels like handing a kid a Christmas magazine to be circled for presents only to find that not only was nothing circled but the magazine wasn’t even open!\\\\\\\\\\\\\\\*\\\\\\\\\\\\\\\*

I’ve been having doubts about marriage and a long term future because I’m always subconsciously upset that we aren’t living our sex life to the fullest while we are young, have our own space away from family and don’t have children running around. A healthy sex life is extremely important for me and it feels like that itch hasn’t been scratched in a long time whether it’s the frequency of sex or the intensity.

I’m more of a switch, being dominant half the time and submissive the other half depending on how I feel that day which to me is just double the fun. After a discussion yesterday, I asked if she even liked being dominant and she said “no”. I’m not going to lie, it stung me a lot especially since I’ve gotten her to be dominant a few times and she even seemed (to me) to have been having fun at the time during those sessions. Hearing that something so important to me doesn’t mean the same to her was interesting and I’m still not sure what to make of it.

She has every right to be vanilla and want sex less frequently but I’m catching myself being frustrated and angry more and more often at the frequency and intensity, it feels like pulling teeth from her almost. I will never and have never taken it out on her, it’s just my own mental battle at this point.

We have toys and vibrators, I will always make sure she orgasms first and has had her fill before I finish and tap out as she is and has always been the priority for me during sex, not myself. There is only so much missionary with a vibrator and doggy rotation I can stomach before I get bored. We’ve discussed me masturbating to scratch the itch but I really don’t like to as I feel so much further and distant from her on days that I take care of it myself instead of just having her be involved, it doesn’t even have to be sex, we could just masturbate together and I would be happy with that.

Im fully aware that sex isn’t the end game of a relationship and the only thing to strive for but she is so perfect in every other way it makes this feeling so confusing and conflicting, any comments or ideas?

TL;DR unsure about sexual chemistry and connection after 4 years together, don’t know what to make of it.