How do I end this vicious cycle in a healthy way.

For years I just keep going through the same cycle, I'm sorta happy but more like content in the moment, then I'm sad, depressed and feel completely and utterly alone in the world. Then I get really angry, at everything and nothing at the same time. I become rash and fly off the handle easily. Then I go back to being ok and content for a little before the cycle begins again. The cycle can last from hours, to days to weeks, and is completely unpredictable. It's like I can't control my own thoughts and emotions and I feel so trapped and alone. Don't worry I'm not feeling like ending it, don't want people to worry. I could never do that knowing it would cause others pain. I am content to live in misery before giving others grief, if that makes any sense. I'm just tired guys. I feel strung put and exhausted and sleep can't fix this emotional exhaustion.