Pretty much what Casual in #4 said. Try to change up your habits, do something that breaks your routine and lets you see outside of the hole. I recommend doing some sport (if your not already doing so) as a start so your body will produce some endorphines. That may clear up your view a little bit and give you some headspace to work with. Figure out a personal goal that you can look forward to and strife to (doesn't have to be big at the start, maybe its just walking around the block once a day for now), establish multiple different activities that keep you busy, express yourself. Just a few ideas.
Also, remember that its ok to be unhappy and that you CAN change that if you really want to, you have the power to do so! Not saying that its easy, especially if you have established a lot of unhealthy habits, but there is a way!