blackout? what happened?

Well, I was with my friend and her dad and step mom at a tattoo shop. i was hanging out watching the tattoo laughing and i felt fine. i was sitting on my friends lap when i started getting sick, randomly.. i blacked out, and my vision started comming back i felt the need to puke so i stood up.. when i stood out the black out got worse and i started like kinda feeling heavy and i couldn't stand so i sat on the floor with my head on her knee and i was sweating really bad she said it went all through my hair..

then i sat over the toilet but nothing had happened..

i keep feeling lightheaded now, with really bad headaches

any answers?