Is it normal to bleed every time u have sex?

I lost my virginity to my boyfriend of 4 months. We have been having sex almost once every week. Everytime we have sex we go really rough and hard. Then when I get home I see that I'm bleeding down there. It's not a lot but it's still blood and I thought that you only bleed from your first time. I'm not sure if having rough sex can cause this. Please advise me !! (17)