Hon, here's a few things you might've overlooked -
Anti-depressants can change your metabolism, make you gain/lose weight. They sure did for me when I was being treated for anorexia, that's why I came off 'em! The older ones are worse (Zoloft, Prozac, etc) so if you must use them, try the newer types (less side effects - Celexa/Venlafaxine, etc.) Or go herbal - St John's Wort is great for depression, I'm on it now, only real side effect is you must be careful how much you expose yourself to the sun (more than normal) it changes your skin's melanin levels, could increase chances of cancer, etc.
Alcohol - FULL of calories. You can't help gathering a beer gut, no matter how much you exercise, sorry!
You've said it yourself - you can resit these things. Some poor buggers don't actually have the chance to even take them in the first place. Think of people with Motor-Neuron disease, or MS, or terminal cancer. I know it's the same cliche, but its the truth - LOOK AT WHAT YOU HAVE!! You're still young, so it's so much easier to turn your health/whole life around. You've not got a family to look after, so thats one less obligation. You're in debt, but thats a reasonably small one compared to some others! Keep wasting your cash on drink/PC games and yeah, you can stay in debt. Or you can fund it into exercise hobbies, get fitter, making it more likely that people will want to employ you coz your health won't make you a walking timebomb and thus a liability to employers. See what I'm getting at?
Give it a go, mate. Look at what you already have and expand on them. Good luck, let us know how you do.