It is fairly common that a medication that previously worked stops working. Thi may be due the changes in one's brain that affects the mechanism of the medication. Oftentimes, increasing the dose of the medication improves its efficacy. Other strategies, switching to a different class of medicines, combination of 2 antidepressants, medication and psychotherapy.
Major Depression is a disorder that has a high chance of recurring.
There's only so much that drugs and psychotherapy can do.
You and I have a soul that is empty without Christ.
He can fill your soul if you'll ask Him. I'm not telling you to stop taking the drugs, etc. You may need to for some type of imbalance. It's just that when the physical stuff is taken care of, it only leaves whatever may have triggered this whole thing in the first place, like abandonment, emptiness, isolation, abuse, etc. Only God can heal those things.
Take Care,
Carol.