I Am Not Sure If I Am Pregnant Because I

i am not sure if i am pregnant because i never had sex but my boy friend had put his sperm on my butt, i started stressing since then if i would get pregnant and did not get my period since then. That happened a week before my period was actually supposed to start but now I am three weeks late to get my period. This Sunday I thought I had some bleeding but I am not sure, and I had diarrhea today. I am really stressed, I dont feel tired, did not puke. Can I be pregnant? What is the safest way to abort if it is my fourth week? What should I not do after aborion?