Welcome to the site, you have found a great place where people truly care about each other!!!
I have had depression for over 21 years so I can relate to the fact of meds. I know in my experience that meds do lose their effectiveness over time, it is referred to as building a tolerance to them.
I am not sure how severe your depression is but for me I am at the level of treatment resistant depression which ia the "grandaddy" of depression. For me, I have the VNS implant. It seems to be working and I take one med as opposed to recent years of over 4 or 5 meds at a time.
Good luck and keep your faith!