yes, DP/DR can be a symptom of severe anxiety and depression. I've had several episodes of derealization, beginning in the fall of 2012. One thing I can assure you is that you are not going to be insane, and the other thing is that you can pull yourself out of it. But you have to realize that it will take time and work to heal, it can't be done overnight.
Tell us about your current drug use. I guess you ceased to use psychedelics (which is of course very necessary), but what about other things? I understand that you use opioids, but if you use cannabis as well, you should stop this instantly.
In general you should minimize your drug use and get healthy. No coffee and cigarettes, they are stimulants and might worsen your anxiety, which contributes even more to your DP/DR symptoms.
What's most important is that you go out and do stuff, to distract your mind from that obsessive thoughts. If you are at home all the time, your thoughts just go into loop mode and you'll never be able to relax. Meet up with friends, ride your bike every day, do some other form of exercise.
Exercise in general is very important as well, as it makes your mind healthier as well, so do something everyday, even if it's just a little bit of jogging.
You should also improve your diet, eat healthy and proper food, and maybe pick up some supplements. I can recommend Omega-3 and Magnesium. Drink plenty of water and avoid sugary stuff.
I guess this is a lot of advice, but well, I've been where you are. It's a very shitty situation, but you have to remember that
you are not going insane. If things still get worse over the next few weeks, you should consider getting medical help, and maybe therapy as well, if this is possible for you. You also have to realize that you cannot escape your thoughts and the more you try, the worse it gets. Just try to let them be there and try not to fight (not easy, I know, but you have to learn it). Also look into breathing techniques, they can help you to relax.
well, if you have more questions, you can write here or also send me a PM.
All the best