Do you use any type of lubrication and did you feel any pain during sex?
I remember in another post you were saying that you were getting an unusual discharge, but you didn't answer any further questions about it. If you did have an infection, then you may experience bleeding after sex.
I'm not really understanding why you're having so much unprotected sex. Condoms are cheap and birth control is available for teens at low cost or free-- if you need help with these or have questions then I'd be happy to help.
You may want to consider Plan B, which is an emergency contraceptive that you can take up to 5 days after sex to prevent pregnancy.