Hey,
You should probably talk to your doctor at your next visit. My doctor told me to stay away from “excessive heat”, and your body heat plus your partners can just be over heating you. Which in turns makes you black out or faint. Maybe, you could keep a fan on, open a window, drink some orange juice quick after, or even some water. Lol. You should also be drinking alot of water. If you don’t consume enough H20 then you are more likely to faint, because your body is dehydrated.
And you should ask your DR if its normal or not. That is the best advice I can give you, when it doubt…as the doctor.