What Causes Sudden Dizziness And Blackout After Intercourse?

Hi, so me and my bf were having sex and after i went to the bathroom to clean up well I sat down on the toilet and started to feel really dizzy I was sweating I felt nauseous and everything was going black and then coming back well I got up and started to walk back to the bathroom then I felt really weak my ears were ringing really loud my bf came out when that was happening and I started to fall to the ground I remember him talking to me but I couldn t respond he said my face and lips were really pale my pupils were huge and I stares off into some kind of daze but I couldn t respond to anything.