Folks, the OP has asked that people stop mentioned that particular type of sex please, it may be a trigger for her so please respect her wishes.
OP, in your position I'd mention you've had previous bad experience in sex but don't go into any more detail than you're comfortable with. Ask for a slow approach, romance, cuddles, intimacy rather than sex. Given your past awful experience it might be useful to use the question of whether you'd be happy simply sleeping alongside him, as a test for whether you are ready for anything else. Then maybe suggest you try non-penetrative sex first and stick with this until you feel comfortable taking it further. There are plenty of things you can both do that are fun and build trust and intimacy. His reaction to these 'stages' will also help give you an indication of whether he's a decent bloke.
You could also write a list of ground rules including the things that should (hopefully) be obvious, like no sex whilst you're asleep. You could share that, on paper if you felt more comfortable, and then discuss. Hopefully he'd be horrified at the very thought, and it might be a gentle way to give him an idea of what you've been through, and where the danger areas are. You could also, at least for your own reference, write a list of what is ok, what might be ok in the future, and what is a definite no for you. It's up to you whether you share that outright, or just use it to organise your thoughts.
I would recommend you discuss your history more fully before moving on to full on sex. Ask him to check in with you for enthusiastic consent at every step in case you freeze and aren't able to articulate a 'no'. My worry, as someone who has PTSD and been triggered by unexpected things, is that something could trigger a flashback or reaction which you may not be able to articulate in the moment, and he may not understand what's happening. If you've any history of flashbacks or panic attacks, you could talk him through a grounding technique that works with you to help you if something is triggered, even if that is cuddle me/get me a glass of water/don't touch me/talk to me. I understand you might not feel comfortable having that discussion now, but if you work through the earlier stages of increasing intimacy and he's aware that there is some difficult history, then by the time you get to penetrative sex then you may be more confident to share, and frankly, if he has any perception at all he will be expecting something like this and be prepared to do whatever is necessary for you to be confident and comfortable.
Good luck, and have fun.