Why am I not losing weight anymore?

You're body has become adapt to learning how to utilize the energy you give it, therefore, your metabolism begins to settle. And as those 3 miles begin to get easier, try jogging and building up the intensity to be able to start running 3 miles. Trust me, I know where you are right now. I was pretty out of shape last school year, but I lost alot and now I run for the school's track team. Well good luck!