I am sorry to hear you are down.
Thyroid wise, all you have to do is ask your doctor for a thyroid panel (blood test that checks for thyroid hormone levels like TSH, T3, T4, etc). People with low thyroid functions tend to gain weight easily and feel tired/sleepy.
I don't know if this will help, but I do get depressed too (more bored than depressed I guess, but they feel kind of similar to me) and when I am, I try to find things that make me feel happy (and like you said, watching the same old doom and gloom news on TV doesn't help.)
One of the things I like doing is to write an appreciation list (I know, it's kind of corney)- List up anything and everything I can think of (people and things - house, car, furniture, weather, stores) and write down why I appreciate them. (Like bbbam said, counting my blessings really does help.)
Then I go onto a list of what I want in my life that would make me happy at this moment, and why. It could be anything - small or large - material things (without worrying about if I can afford it) or things I want to do. Then I feel the feeling I would get if I had these things or if I were doing these things. That really gets my mind going and it usually lifts me up. Sometimes by doign this, I find things that I didn't even know I was interested in doing, which opens up new possibilities in my mind.
I hope this helps...