What he said.
If you actually ejaculated just from the top's wet, throbbing cock head nestled against your boy-hole, with no penile stimulation at all, you have the answer in the puddle. Without any health information, the rough chance of transmission is 1%. You said they're poz, but are they on meds? LOTS of guys are living "undetectable."
I don't share the mystical approach to HIV, so I've chosen PrEP. I'm still not perfectly protected, but the odds are small enough to enjoy fucking naturally.
There really is something about sinking your cock balls-deep into a well-used, oozing, hungry boy-hole on first attempt. All of the bottoms' accounts say they love the way it brings out the animal in the tops. The tops just immediately go for it, planting their seed deeply and urgently, and both love it. The instinctive need to breed and complete abandon of any pretense, probably losing track of where we are and who's around us, takes us close to nirvana.
Oh, except if you have a special guy who's right there with you, urging you to breed the boi strapped to the bench. Making out with your guy, maybe he's "resting" his hand on my pounding cheeks, just gently hanging on, witnessing the breeding, or fondling a pec, teasing the nipple. Mmmmmm. Blast off!