about 4 weeks ago i had unprotected sex with a friend of mine. we live in ontario in a city with about 73000 people in it. before me she has had unprotected sex with about 3-4 other guys. i was inside of her for about 20-30 minutes. after we finished she noticed that she was bleeding a little from her vagina.

1) what are my chances of being infected with hiv?
2) is it likely that i was?
3) should i be this freaked out about this?

please help me if you can. thank you in advance