I cheated and now I'm pregnant

last week my bf went out of town for his aunts funeral and I didnt go because I have school. I run into my first kiss and one thing led to another.. We had sex. I cheated on my BF and I feel bad bout it. I dont know what to tell my boyfriend when he gets back and to make matters wourse I think Im pregnant. We used a comdom and he pulled out (Im also on patch) but I got my period right after and it was much heaver than usual. we also did anal and he didnt wear comdom for that. I know I used protection but pre cum is a thang and birth control isnt 100 per cent. Also I never blead this much and Ive heard of people still gettin their period when they are pregnant. Should I tell my bf I cheated or should or just tell him the baby ishis? Also the guy I cheat with is 22 and I'm 16. Does this mean I am raped? I didnt want to do it anymore because I felt guilty but didn't say no but he is still older. Help!!