Don't feel bad, I think the most I ever weighed was 147, danged close to 150. My labs were bad and doc told me I had two choices. One, take statins even though they gave me bad side effects or lose weight and change my eating habits. I chose the latter. He told me I had motivation to do it and I did. It's hard to lose weight and exercise when you are in pain. Yesterday, DH wanted to go for a walk as he is trying to lose more weight. I told him I'd go even though my foot is a flaming mess of pain right now. It was, 'slow down, dear....OUCH!' Every ten feet until I realized that he was behind me and he was telling ME to slow down because his knees were hurting him.
My SIL is doing water exercises and loving them. Something you might want to look into for your knee along with swimming.
@ShrekDawg. Not good to be losing height at such a young age. Talk to your doc now rather than later. You are too young to get a bone density test done but he might recommend that you start something like Critical or some other calcium supplement along with vitamin D3. Losing height means that you are losing bone, usually in your spine.