Anal sex, pregnant?

Ok I'm 16 and me and my boyfriend *attempted* anal sex about a week ago. I use the word attempted very loosely because he didn't really try to put it in. We were just messing around. I don't think it made him necessarily ejaculate . Maybe a little? But I didn't feel anything wet. I heard that the semen could potentially dribble down to the vagina but I didn't feel anything! I am worried because my period is late. It's July 29th and my period would usually arrive around the 20th of every month. I have had my period since 8th grade so I know it's not because I haven't had my period for a while. One time months ago my period came really late. It came in the beginning of the next month, I kid you not. So because of that, I don't know if it might be a little normal for me? I just don't want to be pregnant. I am extremely scared. I am a virgin. Same with my boyfriend. We've been going out for almost 3 months. Please don't think I am a bad person or anything. I feel terrible about doing it anyways and we didn't even have anal sex! Please help me. I'm so scared.