i've passed out quite a few times from my period. sometimes the pain is so bad, that you can actually make yourself pass out. i've done the same thing in the bathroom and hit my head on the shower also. i wouldnt worry about it too much, just make sure that when you do feel like you might pass out...you try to breathe slower, and tell yourself you wont let yourself pass out..i talk to myself and it actually passes. make sure you keep yourself hydrated...if you are in such severe pain that you cant take it, i would suggest going to the dr...i think you will be alright though, as long as you aren't hemoriging, or bleeding serverly while passing out or after or during...