First: do sincere tawbah (ask for repentance from Allah). Pray two rakah nafil and beg Allah to forgive you and give you the strength for whatever is lying ahead of you. Ask him not to make you pregnant (as Allah can give and take as he chooses). Second: establish whether you are pregnant or not. Buy a pregnancy test, most detect pregnancy within the 1st week. Go and get a blood test done if necessary (you don't need to tell anyone you are not married). Blood test is a 100% accurate, though most pregnancy tests are 99.9% too. If you are pregnant, then worry about the third stage.