Or the drugs have been causing the depression and therefore no longer give you effects. It happened to me, it has probably happened to almost everyone here I think. It takes time to see it, at first you will refuse to believe it. But try to take a break, and I don't mean a week or two. Depends on what substance you have used of course, but I recommend trying half a year sober at least if you can stand it. Which I don't see could be too hard, if the drugs are no longer fun. Then it's just a waste of health, time and money.
I wish you good luck finding the path we all seek, to true peace and happiness, artificial feelings caused by chemicals tend to have the opposite effect as time passes.
Drugs might often make you feel like you are numb emotionally, you may misstake numb for happy when anxiety etc fades, but soon you will notice that the things you once enjoyed, they feel numb too. At this point it's not that great anymore. Life becomes nothing, at which point I got depressed.