Help and serve others and you will forget about yourself. Have you ever met a good Samaritan who was unhappy? If you see someone with car trouble, pull over and help them. Try it for a week and see for yourself.
Having said that, I agree with
@Baldingtooyoung that you should take control of your life and maximize what you can. Make a list of things you want to accomplish (e.g., gym, eat healthy, get your degree) and just focus on that damn list; man up and get it done. You'll be too busy to think about how "your life sucks" amidst all your goal achievement and helping people. If you do this, I PROMISE YOU you'll life will change dramatically. What do you have to lose? All of this is within your control regardless of what hand you think you were dealt.
We all want you to succeed and be happy. We need more good people in this world.
I want you to keep us posted on your progress.