dizziness after sex?

I was receiving oral and was laying down when I opened my eyes the room was kinda spinning like it would if you were drunk, it lasted only a few seconds and I didn't say anything and kept everything going. After we had intercourse i got up to get a drink of water and i felt the dizzy spell again i couldn't even stand straight. Has this happened to anyone? I got really freaked out and said something finally about both times I felt the dizziness so he ran to get me cold water. We have been together since I was 14, I'm 27 now and we have a two year old daughter if your curious.