Ask Dan & Jennifer

if you look the bleeding concept after/during sex on the internet, you will find very good information.
your best bet is that both of you were a little extra ruff, and nothing serious is occuring. kinda like a sex battle wound lol!
if she is in pain, stop!!! if she doesn't feel anything is wrong, then just take a slow and more gentle way towards her.
talk with her. see what is going on with her body by asking her 'does it hurt?'
see how much blood is perent. see how long the bleeding last. see what color the blood is.
all these factors will help you both determine what may be going on. a trip to her woman doctor will also be greatly advised. both of you will be assured in knowing the full medical evalution.
personally, this happens to me fromt time to time. my body changes during my monthly cylce. sometimes, my inner's (lack for a better term lol) get smaller, and my nicely sized man's member 'tears it up' lol. (i hope you wont find these terms offenssive in nature!) i bleed a very light tinge that shows up on the toilette paper. this goes away within hours though, and i feel absolutely no pain.
i hope this helps some what...