Unprotected anal sex, pregnancy scare

Hi everyone, I'm 17 and my boyfriend and I recently experimented with anal sex. I lay down across my bed facing the wall with my vagina on the bed and him behind me. We were at it for about 15 minutes in which my boyfriend did not cum and we stopped. We were just trying it out. Now, it has been two weeks later and I am so scared I might be pregnant, maybe I am just worried too much. My breasts are sort of sore and I have a little bit of bleeding but I think it might be my period coming up. I am so scared...I haven't had any other symptoms at all and I am not tired, do not urinate alot, not sick, and I feel normal otherwise. I am not sure what days my period occurs because it is sort of irregular. I can't have a baby, I am so worried...what do I do?!?!