Not sure what's going on.

The last time I had my period was May 22-27. I am 18 years old. I have taken 2 different types of pregnancy tests and they both came back negative. I don't know what to do. I don't think it's very normal for this to happen. I don't know if I could still be pregnant even if the tests say I'm not. I really want to go to the doctor to see, but I can't because of my mom. Anyone have any ideas of why this would be happening?