Weight loss...

I recently quit smoking, the weight just kinda came out of no where. I don't feel like I'm eating more (scheduled meals, not larger portions either) no other changes that I can think of. But I want to put an end to this gain before it gets out of control. I only need to lose about 15-20 pounds ( I think, I was 125 before and I'm 147 now-- I'm 5'4") Any tips? Suggestions?