Hi Dia06!
Glad you're joining us! Did you come up with any possible explanations for why you're gaining? I know that if you are losing fat while gaining muscle, muscle weighs more than fat, but when I think of that, I think more in terms of weight-lifting. From what I've seen, walking usually causes people to lose weight. Are you on any kind of a diet plan along with the exercise? I do hope you get it figured out, and if anyone can help you, I'm sure the people here can! It's a great community!