Don't be sorry man. It can be tough digging yourself out of a hole. But at least you are aware of the problems you face. (possible addiction/reliance on drugs, sleeping pattern way off, etc).
Prescription drugs are the worst kind, in my opinion (except for heroin). Because people think they got it from their doctor, so it must be safe. I'd say that prescription drugs are far more dangerous. Especially psych meds like SSRI's. But that is another debate.
You are probably feeling depressed because your brain chemistry is off. That is where diet and exercise come into play, to help you balance all that shit out. Exercise with heavy weights will increase your testosterone levels and that alone is worth it from the feeling of confidence it gives you. You just have to get the momentum to change your life. I know its cliche, but one day at a time. Stop taking the ambien and grab those weights. Check out my exercise thread for advice or message me for more personal one on one. I have a combined 3 years experience (no professional yet) but I can at least stop you from making the mistakes that beginners make.
Go for a run at the park, anything to get out of the house. If you need to be alone, do it out in nature. Don't sit in your house, it starts to feel like a prison because you associate all the feelings of lonliness with it.
If you need to sleep, take melatonin instead. Its a natural hormone that helps you sleep. Go to bed an hour earlier and wake up an hour earlier eveyr day until your schedule is back on track. People that work 3rd shift are notoriously depressed. it's not a healthy time table.
Try doing Yoga. Search youtube for "power yoga mark gonzales" - do that every day for a week and then tell me you don't feel better already. I'd have to call you a liar.