Numbness or Happiness?

It's like I've emotionally flat-lined

So it has been a little over nine months since I started taking Zoloft to treat depression. For the first seven months I felt nothing, no change, no anything, it was almost as though I was taking a placebo. But for the past two (ish) months I have felt...okay. Not desperately suicidal, but not overly thrilled with anything either. Originally I thought "Great! I'm getting better!" but now I'm beginning to wonder if I'm just becoming more and more numb. It's kind of like using weed, in that over time the body gets used to it, so you have to use more and more to get the same high that was attained during the first time you got high. Maybe my mind is just getting used to being depressed all of the time, and it takes more and more to make me as sad as I was. It's almost as though I've emotionally flat-lined, I just don't know it yet. I don't really remember what it was like to be happy, I mean there's "happy" for me, my standards, and there's everybody else's. I just don't know whose standards I'm at, for my standards I'm fine, for everybody else's, not so much.
There are things that I do that I enjoy, and I smile, and laugh, but there are others that I do, that I used to enjoy so much, and now I can barely stand to participate in.
Of course I barely have a relationship with my mother anymore, we don't ever talk, and when we do it's for like a minute on the phone and then it's done. But in that one minute, all the hurt, all the pain, all the sadness, all the anger, comes flooding back. I saw a picture of my mom today and I cried for about ten minutes, and I'm not entirely sure why. I miss her. In a sick twisted way, I just want everything to go back to where it used to be. When I lived at my mom's house, when I lived in constant grief and anguish. Because I had lived there for sixteen years, and it felt normal to me, the abuse, the constant fighting. By now I'm sure you're thinking "Wow, Nate's totally fucked in the head" Well maybe I am. But why do victims of domestic abuse go back to their abusers? Because being abused was normal to them.