I think im pregnant but, negative hpt

Patient: My period is ALWAYS on time and regular ever since i was ten. My last period was December 3rd today is the 10th of February. I have been experiencing really bad headaches, back aches, cramping, slight nausea, and nipple sensitivity also, a slight pain around my belly button. I have taken an at home pregnancy test results was negative. what is wrong with me ?

Symptoms: Headaches, back aches, Nausea, Cramping sometimes, nipple sensitivity, little pain around belly button ocassionally.