Im bleeding

hi, I just wanna ask, I just had sex with my boyfriend last september 13,2016. he is my first boyfriend. I was a virgin then, but in our sixth try we noticed blood and I was alarmed then we decided to stop. we had sex again for 7th 8th and 9th times and still everytime we makelove there's blood. I am now afraid. what should i do? what is the reason behind?