Aimee, hey. Welcome. (((hugs)))
You're in a tough spot, with a background that makes a lot of what your boyfriend asks really triggering for you, and you're still being brave enough to look into it. I want you to know how awesome that is. Even if you eventually decide this isn't for you, it's great that you're doing some research first.
I want to recommend an angle that hasn't come up on here yet (and to second much of the advise that's already been given-- I love how many suggestions we can come up with here in a short period of time)... There's two authors, Dossie Easton and Janet Hardy (who originally was under the penname of Catherine A Liszt), who have written some of the best regarded books on both polyamory and BDSM. Here are four of their big titles that you might want to check out:
- When Someone You Love is Kinky
- The Ethical Slut
- The Bottoming Book
- The Topping Book
I'll be honest: only the first of those four books is really aimed at people who are "mono" or "vanilla", and both Dossie and Janet (they use their first names to self-identify when writing, so I tend to think of them that way) are very adamantly in favor of both poly and kink, so you have to take them with a grain of salt, but you stand to gain a great deal from their writing if you go slowly
and remember to stop if anything they write triggers you. It might be worth mentioning that Dossie was in a physically abusive marriage early in her life, and that that experience had a huge impact on how she thinks about both poly and kink.
The website www.xeromag.com
also has sections on both polyamory and BDSM, and is well written and much more moderate. It's also available immediately (with an internet connection) and free! I can't recommend that site highly enough-- it's usually one of the first sites people suggest visiting on here, and with good reason.
My other suggestion is to spend lots of time thinking (which you can do by talking and drawing and writing and in countless other ways), and lots of time talking with your boyfriend. I wish I could give you more detailed advice, but it's hard to make suggestions that'd be likely to help without just scaring you more if I don't have information.
I'm so glad you're on here. Thanks for being brave enough to share on here, and keep posting! We're here for you.