Anyone else unable to orgasm with someone else?

I'm 21, and I've been sexually active since 16. I've been with my SO for about a year and a half. It kills me to say this, but I have never had an orgasm with him. Or literally anyone. Yes, I'm a faker. Sometimes I can get turned on, especially if I've had some weed (I smoke maybe 2x a week now, down from every day). Kissing, neck nuzzling, attention to my breasts are all great. But as soon as he ventures down south, any small tingling I had just vanishes. It doesn't seem to matter what kind of touch it is, I just freeze up. What can really get me going is going down on him, but he just doesn't last long at all and if I try self-stimulating, it feels like...nothing. It's just so incredibly frustrating. I want to have a healthy sex life!

We're both not very verbal people when it comes to sex. I don't know how to talk to him about this at all, it makes me very uncomfortable to talk when he's trying to pleasure me.

I want to clarify one point: I have never been able to orgasm with someone else in the room. ONCE, when I had sex, did it feel pretty good, but I was miles away from anything that I would call orgasmic. What's wrong? I thought that with my current SO the sex would finally be great— he's so handsome and caring, and he has a seriously rocking body haha— but I just can't get going with him there. Has anyone else experienced this?

Edit: thank you all for your advice. I'll try being more honest about what feels good. I think I just get so anxious about how nothing does feel good that I rush through it and don't bother relaxing. So a follow-up question: how do you get turned on with a partner? Is kissing usually enough, or what? I don't want my boyfriend trying to warm up something that's not even on, if you know what I mean.