It's true that the only way to figure out what's happening here, and to ask for the kind of sex you want, is going to be to talk to your boyfriend about it. I get that it can be really intimidating to do, especially if you don't have a lot of practice in talking about sex or other sensitive topics with another person. I do want to specifically note that asking for something sexual, or saying "the way we're doing things isn't working for me right now, can we talk about it?" is a
good and
healthy thing to do in a relationship, even if the conversation feels uncomfortable or awkward.
How's your sexual communication overall? Do you check in with each other often during sex, or offer or ask for feedback on how things are going? Or do you feel like you just aren't communicating much during sex at all right now?
If you want some pointers on how to have these discussions, this article may be helpful:
Be a Blabbermouth! The Whats, Whys and Hows of Talking About Sex With a Partner.