Aysha,
You do realize that using causes depression. My son was seeing an addiction psyciatrist and was just beginning to figure out his triggers, but was not ready to do the work. His
psychiatrist told him that even if he stopped the drugs, depression would be a part of his life for at least a year. I guess that's how long it takes for the chemical imbalance that using causes to work it's way out of your system. Some people use because they are depressed, rather than deal with the depression, they mask it. The chicken or the egg? You will figure it out, but probably not without support and working a program.
Good luck.