Advice!!!

So I'm 20 & I've been sexually active since a month before my 17th birthday. I haven't told my mom and I'm afraid too. (Hispanic Mom's are scary) How do I tell her? I went to the doctor with my boyfriend and we talked to the doctor about birth control & I really want to get on some type of BC since I'm in college and I'm not ready for a kid. Should I just to go the schools clinic & get on some type and wait until I'm ready to tell her? Also she's mentioned BC to me (IUD), could it be that she kinda has a clue I'm sexually active? Also I go through really bad cramps so it could also be why she mentioned it