I will tell you about my grandfather, who was allergic to exercise and vegetables as he said, and for him it was a slow death because he did not take care of himself. It was about 20+ years of dealing with various physical ailments from kidney disease, diabetes, COPD...and mostly because of not taking care of his health. So I say if you want to avoid a slow death, definitely take care of yourself. If you exercise and take care of your health you will not have as many physical problems as my grandfather did. This is what motivates me because I don't want to deal with what he had to go through.
The other thing I want to say is don't exercise for the purpose of looking good or getting laid because that will just get you more frustrated. Do it for your health and do it for the mental health benefits too. Exercise is good to get out any anger and frustrations without hurting yourself or anybody else.
I am sorry you are having the suicidal feelings. I have been there and it's definitely rough when you have lost all hope. Keep on fighting. I am rooting for you