Weight issues.

For four months now, I have been reasonably active and commit to eating healthier and walking in the afternoons, but I am seeing absolutely no positive changes in my body, if anything I have gained weight. I am so insecure and I dream about being fit and aspire to be a personal trainer.
Can anyone help me, or give me any tips on how to get fit and gain muscle and lose fat?

Excercise or something like a treadmill 2 time a day. And, cut out some, but not all junk food, cause too dramatic of a change could make u gain weight