Your situation is not unique; I hear the same complaints often from other recovering addicts. I've also heard similar comments from people after they taper off Suboxone. Some people describe a chronic, painful 'emptiness' that was present before using opioids, and that returned after opioids were discontinued. People sometimes discuss whether buprenorphine, the active part of Suboxone, fills the 'hole' or empty feeling that is part of borderline personality disorder.
I encourage you to avoid 'euphoric recall' about the active using days. People often forget what it felt like to spend your last 80 bucks for a buzz that starts to wear off almost as soon as it starts. They forget the hopeless feeling after promising themselves that they would stop, but then using again. They forget the misery of withdrawal that is there most days-- hiding in the bedroom when the inlaws are in town, with everyone wondering why dad is sick yet again... They forget about being broke all the time, and having no interests in life other than finding and scoring dope.
Unless you are very unique, you were miserable when you were using. Try to remember the entire history-- not just the moments of relief that never lasted very long.
I don't know if you have a chemical deficiency; I would not expect that after opioids, but cocaine depletes the 'happy transmitters' in the brain, sometimes for weeks or months. Make sure you are eating well and taking vitamins, and getting a regular, 8-hour night of sleep.
There are many things going through the unconscious in early recovery; shame, guilt, sadness, mourning the loss of your 'romance' with the drug of choice, fear about the future, etc. It is hard for a person to be aware of these thoughts, as they have been repressed for a long time and won't just 'pop out' now. I work with patients to practice feeling those emotions again-- and it takes time to learn to identify and tolerate the vulnerable feelings in particular. A recovery program such as the twelve steps can help with those types of things.
You might be clinically depressed-- and in need of treatment. SSRI's work in most people if the dose is high enough; people usually stop them before getting to a sufficient dose for a sufficient length of time.
Finally, realize that your new life will be different from the using life. Your mind no longer is preoccupied with just one challenge; now you are aware of many challenges. It takes time to grow into sobriety-- but the eventual outcome is worth the work, and the wait.
Just stay clean, and good things will happen-- I can promise that. But consider treating your depression if things stay down for more than a couple months.