The drug you are on doesn’t work for a lot of people for depression, so that is not uncommon. You have to try a lot of different drugs until you find one that works. Some add drugs like adderall also have an anti depressant effect, so you might want to try that. As for what it is, whether the ADD or depression, not sure it makes sense to separate them. ADD can cause depression, but it is still depression. And regardless of what caused what, the key is finding a treatment that works for you. This likely means trying lots of different medications, and possibly going to several different therapists. In the long run what treatment works for what person varies so much that it won’t be very helpful to know which came first.