No period in 3 months. Not prego.

Okay so I haven’t had my period in 3 months. At first I freaked out and took a test. Negative. I happened to go to a doctor for other reasons and they took one and it was negative. I took another one at home a month later (about 2 weeks ago). Negative. So it’s been like 3 months now and no period. I stopped taking my BC about 2.5 weeks ago and still nothing.... I had cramps a couple days this week but still no blood. Any advice?