I doubt the use of recreational illicit drugs will have been the cause. SSRIs actually simply work to block at least some of the action of most stimulants.
Alcohol however, especially since you say you drank quite heavily, is the thing that flags up for me - it can increase side effects of SSRIs such as dizziness and poor coordination and is just generally very toxic. Once when I drank far too much I stayed sick for a solid month after the effects of the substance itself wore off - my hands were shakey and I had bizarre hearing/orientation problems.
Almost 3 years is a long time. I haven't known anyone else to have lasting effects like this from Sertraline (I was on it a year myself, but I didn't drink), I'd find this worrying and want to see what a doctor's opinion of the situation was.