Hi, dman,
And welcome to SR and the MH forums!
I don't find it unusual that you're depressed or that you are having trouble remembering. You've been ingesting chemicals that have been messing up your brain's natural chemicals. It's likely that when you get past the withdrawal, and *if* you stay off the drugs, your memory will return to it's normal state.
And the depression will likely lift too, unless you were depressed to begin with. Many times, people turn to drugs to self medicate. In other words, they have a mental health issue, and may not realize it, and turn to drugs to alliviate the symptoms they are experiencing. So, if you've been clean for some time, and are still experiencing depression, you may want to see your doctor.
In fact, it might be a good idea to see a doctor anyway. Tell him/her what's up; what you've been doing and get a clean bill of health. A counselor could be a good source of support while you are working though all of these issues. And NA certainly would be very helpful as you work to live a clean life.
I wish you the best of luck. Please feel free to stop by on the substance abuse boards too. There's lots of good people here that can help you on your journey. Stick with the people who have what you want -- sobriety, a clean life. They have the knowledge to show you the path.
I look forward to getting to know you.
Shalom!