3 months late negative hpt

So not to be weird or anything but in November I started the first and ended the second I didn't have another period for 50 days and then had a very light period for 4 days December 23-26 and I haven't had a period since but i took two hpt and they came out negative and in December I got a urine test by the doctor and it also came out negative! I've been eating way more and have lower back pains and mood swings all the time. My boyfriend is really starting to worry PLEASE GIVE ME ADIVISE!!! Really really need other women's info!!