Hi there salasss,
Technically, it is possible to have an involuntary orgasm (when you're not necessarily aroused and/or wanting to), but if I understand your question correctly, it seems like the situation that you're more concerned about is one in which you aren't feeling aroused or 'into it', but don't want to hurt your boyfriend's feelings.
You said that you've talked with your boyfriend about this before - have you tried talking to him during times where you weren't feeling aroused or didn't want to have sex? Has he said something that's made you feel like not having an orgasm, or saying no to sex would be terrible?
At Scarleteen, we generally advise against faking orgasms, because it's sort of a band aid fix to a bigger issue. It may seem like a good idea, because it means that in that moment you don't have to tell anyone that you're not interested, not aroused, or not having fun, but what's really happening is that you're not getting what you want (pleasure, honesty, or an actual orgasm), and neither is your partner (who thinks that this is a mutually pleasurable experience and doesn't know that you're not having a great time!). Heather explains this in detail in
A Faking Farewell way better than I could , so it may be worth taking a look at.
Also, if you haven't already, you should check out these other articles (some of our most frequently recommended ones here at Scarleteen):
Driver's Ed for the Sexual Superhighway: Navigating Consent and
Be A Blabbermouth: The Whys, Whats, and Hows of Talking About Sex with a Partner, and
Sexual Response & Orgasm: A User's Guide.