Why am I having intense cramping in my uterus?

I just started to get cramping in my uterus I think? the area above your pubic bone. Well I am not sure as too why? I came home and ate waffles I had some Carl's Jr at around 5 pm then went to the gym. Could it be cause of that? I know I am not pergnant. Unless Ive been preggers for 6 months without knowing it! Which is highly unlikely :-/ Someone help me out here!