I've had my own trauma to deal with and I've played with a number of people who have trauma. You can't guarantee that it won't get triggered - what you can do is try to be aware of and manage that risk and do your best to make sure it's dealt with in a supportive way if it comes up.

A few ideas:
- As a way of doing bondage that also works as a safeword I like "If you take your hands off this thing (headboard, wall, chair, etc) then I'll stop fucking you" - this is great because it works as both a threat and a way to opt out
- If you're going to do impact play that will release a lot of happy fuzzy brain chemicals but also might trigger trauma then make sure he checks in with you in a way that's meaningful and direct; I particularly like the method of stopping what you're doing for a minute and bending over to have a 1-minute intimate conversation. Can work to both edge on the play by being a tease and also make sure everything is going how you think it is (which is hopefully good!)
- Stick to using "No", "Stop", and "No more" to mean what they really mean. You don't have to use obscure safewords to do kink, you can stick with basic language. Also make sure it's clear that "maybe", "I don't know", and "I'm not sure" don't mean "yes" - instead these can be a great prompt for sexy teasing that can usually push out either a yes or no.

I would also strongly suggest that if you're not doing it already, counselling is a very good idea. Counselling gives you somewhere else to talk about your trauma so that you can work through it while you do your kink stuff with your boyfriend. If your counsellor isn't kink friendly then stick to talking about your feelings about what's being triggered within the initial trauma. If you can't afford counselling then check in your area to see if there's free or sliding scale counselling, which does exist (for sexual violence trauma a lot of women's centres offer help).