For The Past Few Months, I've Been Feeling Super Down,

For the past few months, I've been feeling super down, then normal with a few elated bits thrown in, then really upset. It is usually in that cycle, and he sadness can last for anywhere from a few minutes to weeks on end while the normal usually only lasts a few days. The elated bits only seem to appear while I'm feeling normal, and they only last for a few minutes to a few hours. I have no idea what's going on, can someone help?