Pregnancy

Has anyone been on the depo shot and been told they could become sterol? I was on it for about a year and a half and was then told I could have a 50/50 chance of being sterol. I have been with my boyfriend for a year now and have not been on any kind of birth control and we don't use condoms. He has came in me many many times and I have not missed a period and all the tests come back negative. I feel like I'm not going to be able to get pregnant, what do you think??