I need help

So I'm 16 with a strict stepdad and somewhat bitchy mom. My boyfriend and I have been fucking since October, and my mom knows this. We have sex like twice a week. This week I'm Supposed to be on my period, I am on birth control. It started when I went to bed Thursday night and I bled like I was supposed to Friday. Today all I had to eat was several bowls of cereal until 11 that's when I ate hamburger helper and a biscuit at midnight but I haven't bled all day just spotted. I am scared and I don't know what to do. My periods normally last 4 to 5 days.