Anyone know what may be causing irregular periods?

My periods are like, anywhere from weeks to months apart, sometimes even days, & they last for weeks. A lot of times in the beginning, the blood is sorta black, but as it gets heavier it turns redder & i get clot things. My mum says hers were weird & her Dr put her on the pill & it was fixed. Does anyone know what this is? Some sort of hereditary malfunction?