Ok moms, need help fixing "mommy pooch"

I gave birth to my amazing son June 18th, 2016, at which point I weighed 205lbs! He was very big and the doctor said he stretched my uterus really thin. Now, 15 months later, I still have weight to lose but weigh in at 155lbs. But no matter how much weight I loose this never seems to be getting better! I'm worried I'll be loose and squishy in my stomach forever... P.S. right now I am on a keto diet and have lost 5lbs so far. For work outs I'm doing boxing and swimming. Want to get in better shape before our Mexico vacation in December.