I continue thinking that I'm pregnant because I get my period every 3-4 months but then I take a test and it's always negitive and I feel like I cant get pregnant but my period seems like it gets farther away. I cant actually go to the doctor and find out what's wrong. What should I do? And how can I find out if I can get pregnant or not?

Optional Information:
Female , Age: 15

Already Tried:
I tried going to the doctor but they couldn't do anything beaus my boyfriend wasn't with me and my mom won't give me my medicade card