You're not a downer.
I had an assignment recently in which I made a list of things that I was thankful for. My T says it's a form of psychology called positive psychology, so that I could focus on the good in my life instead of the bad. And I had a really hard time with it. Finally I had to call her to get some ideas, and it's expanded from there.
If you have any hobbies that can be something to put down. You aren't being difficult. I think that when you are depressed it is incredibly difficult to think about something pleasant because it feels like nothing will ever be good again... so what's the point of thinking about anything that used to make you feel great? In a sense, it can make you even more depressed, thinking about what you're missing out on. I get that.
It can be something small. Like playing with your pet if you have one. Taking a walk. Wearing a favorite piece of jewelry. Anything at all. Perhaps your T can help you get started. You see them every week (or however often that you go) so they should know you pretty well. I hope this was helpful.