Tendinitis, or perhaps tendinosis (more chronic degeneration which is perhaps what you have) takes a long time to present itself. It therefore not only takes a long time to resolve but it also will not resolve if the same causative factors remain.
Normal tissue also can appear abnormal if there is delayed repair in the connective tissue system. Often we can think of this as a lack of the right fuel to fix the problem. Even if there's good food going in it does not mean that it is getting to that area to fix it. I see this again and again where normal activities cause abnormal reactions.
Of course abnormal lifting and exercises can also cause this so this needs to be considered. Thus far you are telling us you are having local pain relief for a symptom (and not a cause). Perhaps you are also exercising and perhaps aggravating and already aggravated tissue structure/s. I think perhaps it might be time to take a step back and look at your self as a whole system of tissues that are continuously breaking down and rebuilding to work out why in some areas yours seems to have a blockage. Only then will you improve. Hitting the gym right now is not an answer