Is it normal to be so moody?

Is it normal that my mood changes very often during the day? I'm sadboy in my life, that's just my character. But my mood can go up when someone makes jokes. Or just be sad, than for a few mins forget about my problems, became a little happy, and than again back to normal. And this mood changes happen a lot times per day. These changes often happen with a visible reason, but sometimes they occur just for themselves, and they are not so intense, I'm not feeleing like I'm the best and i can fly or drop down so much that I would want to kms. Is being so moody normal? Or do i have..bipolar?(