Exercise for the win, OP?
Sorry about your problems, bro. But seriously... you getting enough exercise?
Also based on genetics, some people need to get a lot of exercise to be healthy.... i.e. some people are genetically built to be workhorses and desk job and no exercise just murders their health.
Edit: I will also second what some people said here... some of your problems may be related to allergies and/or endocrine issues. In my limited experience, a lot of general practice doctors are so good at picking up on these things.
I have an allergy to wheat... my original doctor had no clue that my problems could related to a food allergy. I had to figure it out myself and basically start doing experiments on myself with diet challenges and the like.
As a point of encouragement... it's YOUR LIFE. Nothing is more important in your life than your health. Don't give up, stay positive and keep working for your better health... you can make a big difference in your health with effort.
I'll also second the suggestion of flax or hemp oil... great sources of essential fatty acids... and they are called essential for a reason... you body needs them badly... oh, and they cannot be stored as fat so they are a great way of stoking your fat building metabolism.