I am a diabetic 5'3" and 335. I have lost 80 pounds over the last year but the losssing is slowing down to nothing :( I have had 3 knee surgeries over the past years. I have tried walking but both of my legs give me great pain. What type of exersise can I do to boost my weight loss and not put me in pain? Is there a way to keep from having a flap of skin/fat sag below my waist?