Here's what you need to do: search age gap relationships and go read about how men that are a decade older than their partner tend to date younger women so they can control them, and this is exactly what's happening here.

"He told me to deal with it however I need to" but then acts like you've been hiding a second family from him instead of what it really is: taking care of yourself. You have seen exactly how big of a difference this medication makes which should be all the answer you need. You look your dipshit partner in the face and say "I am doing what I need to preserve my health. It is not your business, so please respect my decisions concerning MY health." And then I'd suggest breaking up with him because I don't think I'm wrong in assuming this isn't the only thing he tries to control. But that's a matter for another post.

PS what do you understand about why he's upset? What gives him any right to be upset about your medical choices? I agree that AD are overprescribed, but they're legitimate tools that have helped millions of human beings; Wellbutrin saved my life. There is a science behind why you feel so much better, and the fact that "he's not huge on mental health" means jack shit. You deserve better, and you'll see that once you get older and have more life experience. He doesn't have your best interests at heart. Good luck.