Fast food?

In the last few weeks I have noticed that I have this pooch. I have been eating fast alot lately but I do not think it is anymore than I have since May. My stomach is sooo big it looks like I am 12 weeks pregnant. I need to get this under control. I always had a naturally flat stomach until when I got the freshman 15 my stomach got a little flabby but never looked this big! Today I could barley button my pants and came undone a couple of times. So tomorrow I am getting some running shoes and tons of veggies to start my diet. I can't do any crunches becauses of my back so I hope that just dieting and running will help get my pants fitting again. If I am pregnant great but I am so confused either way on my bulging stomach and why it is this big.