Advice ?

I just turned 16 in March and i recently found out i am pregnant. I haven't told anyone yet, i don't know how. The only one who knows is my best friend. She insists i wait until i start showing to tell my mom. My mom is a single mom of four and she already has so much stress on her that i dont want to add more. My dad has recently fallen back into drugs again and moved out of state, we still talk but maybe only once every couple months. I know i need to tell someone but it scares me and i dont know how.