Body Insecurity

If you ask anyone I know they could tell you I absolutely hate my body. I get extremely grossed out and I hate that I hate my body because all of my friends are comfortable in their own skin and I'm not. Some of my friends are in the going to the gym and it's great for them but I can't workout it hurts my knees, my back, my arms, almost everything. I hate that I don't just buck up and do it. What do you guys do to get confidence in yourself and be comfortable in your own skin? I just want to stop hating myself.