Mood swings. It interferes with my life?

I have been experiencing abnormal mood swings since i was 15-16 years old. It resulted in me feeling really down at times and unreasonably happy at others. I used to smoke a lot of weed in college as it made me feel better when I was feeling sad or depressed. But recently I moved to a new city for a new job and I haven't smoked in a while. This has caused me to be really depressed and I can't seem to concentrate on anything. I am also having trouble remembering things. I seem to be having a blank mind where I can't seem to get any words out of my mouth. Other times I have so many things to say that what I end up saying doesn't make any sense. My sleep pattern is also affected. Is there any kind of therapy available for whatever I have because I don't want to go back to smoking marijuana on a daily basis as it interferes with my life ?