missed period

It's been 3 days since I missed my period. Me and my bf were having sex in his car and right after my period started. Then my mom found out and mynperiod stopped the same day due to stress I think? Then. I ran away the same day and 5 days later right when I get back home my period starts and it was really heavy. But only last 2 days. I'm really stressed and paranoid about being pregnant? What should I do? I need help asap please. Idk how to get a pregnancy test my mom would kill me if I told her.