Just looking at the drug treatment in isolation may not be enough. What else has changed? If nothing (unlikely as things change all the time!) and it really is just about the biology alone you might like to discuss with your doctor any other alternatives, dual therapy, resistant depression treatments and the contribution of other factors, like inflammation. Coming off paroxetine after being on it for so long is also likely to be hugely relevant in terms of withdrawal, and the timescales on resolution of that are very variable.