Missing AF in two months.

Good morning ladies.

AF's last visit was October 14. In November I only spotted instead of getting a cycle

And the same thing happened this month. I was supposed to start Dec 4-8. My flow has always been regular and now just stopped. I took an test after my second missed cycle and it was negative. I get really bad lower stomach cramps, nausea, and lower back pains. What should I do?