Many Leos suffer from back and spinal problems, made worse by their tendency to be overweight, and their lack of exercise. They get easily stressed and can suffer from heart ailments. However, they also like visiting expensive health farms.
Your trouble, your real trouble, is that you think you know exactly what your trouble is. You have a relentlessly self-critical streak. You doubt your own motives, disbelieve your own promises and question your own abilities. Then, you wonder why you never feel fully confident or comfortable. You have to think positively to combat stress. All you need is to tell yourself that you deserve to be happier and healthier.
You refuse to make excuses for your weaknesses. You expect nothing less than the best and become bitterly disappointed when your exacting standards are not met. So you tense up. You carry your complaints, concerns and regrets like a camel. You see it as your lot in life to struggle on bravely; making the most of tough situations. You suspect that you deserve your difficulties. When others let you down, you may feel deeply pained yet rather than train your anger on another person, you direct a fair portion of it inwardly. It must all, in some secret way, be your fault for being so "less than perfect". So my suggestion is to get out of this self-pity situation and be strong and optimistic. Start to love yourself. You do not deserve this.