Could I be pregnant?

AF is 3 days late, my boobs are swollen, I am nauseous, I am so tired all the time, but I keep getting negative pregnancy tests. I have been having cramps for 2 weeks now but today they have been the worst ever, it hurts so bad, worse than when I get my period. Could I be pregnant even though the test come back negative? My last depo shot was last year in June. I didn’t get a period until october of last year and that was it till my ob/gyn prescribed me proveerá and I had to take it twice and I finally got a period in June, I had another one in July, August, and September so I thought I was becoming regular again. My doctor said this was due to PCOS and that I would have a hard time getting pregnant. I honestly think it’s because the depo shot messed me up because prior to it my periods were always regular and I got pregnant twice pretty easily now after the depo I feel it messed up my system. But could my period be late because I could be pregnant or because PCOS? Anyone with ideas or thoughts?