Which Medication Help To Cure Bipolar Disorder When Experiencing Depression?

Hello, I have a few questions regarding bipolar disorder. I was wondering what medications help the most when the person is in the depressed mode? I realize that lithium is the drug of choice but it also has the weight gain involved too, what other medications would help? the reason I am asking is because I just can't seem to focus, and I'm just not myself. I can't even keep a conversation going. This is not me. I've always been very productive and even when there was a lot of stress I was able to keep a job, but now I can't even keep a job. I was recently fired. I've never been fired in my life. My supervisor said that he felt "I was too distracted" and not really "focused". This was the final straw. I've started gambling to the point where I spend every last dime. I don't even buy groceries and then I feel worse. I just don't know what to think anymore. I am not the same person I was a year ago, not even close. Everything that was important is no longer important and I don't understand why. If you could give some advice or direction so I can fix this "problem" I would be very thankful.