Can I fill in this loose skin with muscle?

Hi everyone, I am 13 months out and I have lost over 150lbs and still losing slowly. I did do cardio exercise in the first 6 months out but after that I totally stopped and know I have alot of excess skin in my legs, butt, stomach and arms. I just started working out seriously. I go 3 days a week and do cardio for 1/2 hr and then I do strength training using the wieght machines. WHat I want to know is if I can fill in this loose skin with muscle or is it too late and if i can what exercise should I be doing and how often? thank you for all your help. Tyshea-Remember only you can make you happy!!! 315/162/150