Am I going crazy??

I feel like I'm going crazy. I had my last depo shot around oct of last year. I always had a cycle on depo, and continued having regular cycles after. My last 2 cycles have been abnormally short and lighter than normal. My last cycle was only a day and a half, and the one before that was 2 days. Before that I had normal 4-5 day cycles and relatively heavy. Along with this abnormal cycles I think I've been having what other women say are pregnancy symptoms. My previous pregnancies I had no symptoms at all. I'm dizzy, nauseous, light headed, and more tired than normal. My husband told me the month before he definitely thought I was pregnant. The last time he and I thought I was pregnant I was. I've taken like 5 tests and they're all negative. I don't know what to think. Am I going crazy? Has anyone else experienced anything like this??? I went to the doctor and he said he isn't worriedz