I'm starting to hate sex again

So I was celibate by choice for two years. Didn't really have a desire to have sex, was kinda mad at men in general for acting like I owed them sex all the time. So I said nope to everyone. Then I met my now boyfriend and I actually felt lust and attraction again so I started having sex again when we started dating. But now it's not like it used to be. It's all about him and I can't even enjoy myself during sex anymore bc I'm bending over backwards to get him off all the time. He knows I don't orgasm from penetration but I still like to do it cuz it still feels good. But I can't even focus on how I feel bc im usually straining myself to do whatever it is he needs in order to orgasm, like suck his nipple. I'm usually straining my neck to do this bc of our height differences while doing missionary. I can't even focus on the sex anymore I'm basically just always waiting for it to be over. I didn't want to do it last night and I'm lucky it didn't become a big thing bc I'm pretty much not allowed to say no, it's just easier to let him do it. Anyways tho I really want to tell him all of this but I'm worried he's going to assume I just don't want to have sex with him at all anymore and that's not true. I still like sex but only if it's both of us and not just me having to please him