This is a medical issue. Learning to take care of yourself is great and will pay off (especially as you get older). But please don't be down on yourself for the past which you can't change. There are many reasons people gain weight. You are now going to do what you can. Self care can be hard at times. Don't emphasize shame; tell yourself you deserve to be healthy and happy.

I had a gastric bypass done recently. if you have any questions, I'd be happy to help if I can :)