What happened to me during sex

Hey B
Me and my boyfriend was having sex and I was on my back he was on top then all of a sudden I started feeling like I couldn't breathe, then I started whizzing then when I got up I was breathing so heavy because I was trying hard to catch my breath I was out of breath 10 minutes Have This ever happened to someone I was guessing maybe I shouldn't lay on my back to have sex the baby definitely wasn't feeling that