Spotting After Period. Negative Pregnancy Test. Have Breast Tenderness, Nausea, Headache, Back Pain

Had a normal period Nov. 1st then nov. 26th early morning started spotting til the night of the 27th then i didnt get my period on dec. 1st and then the early morning of dec. 22 i started spotting again i thought it was my period but now this morning the 25th the bleeding has basically stopped. I have taken test and they are all neg. went to the ER and they did a urine test but not blood test the doc said they were the same so neg urine test and all other blood work says i am healthy. I had all the symptoms breast tenderness, nausea , headaches , backaches, flutters in my tummy and i feel pregnant but thats not what the tests say. What else could it be?