sexy time fail (tmi)

Today me and my partner were going about our business in the rest room- hadn't seen him in a long while and he had been teasing me all night and morning. However, all that came to a halt - I felt my heart beating strangly fast and strong and I started getting tunnel vision - OH, IM TEN WEEKS PLUS 2 DAYS PREGNANT FIRST TIMER - and I couldn't hear and I felt so weak - pretty sure I was going to pass out!  We were in the shower so I managed to turn the water cold and it helped. Is there anyone who might know why this happened ? I'm pretty healthy - recently started being able to keep down most of my food. Has this happen to any other ladies?