What Causes Irregularity In Period With Hair Growth Around Breast?

I have a very irregular menstrual cycle, I am 19 years old. I can never tell when I'm going to get my period, it will just randomly come. It doesn't always come once a month either. I have noticed in the past year, I have developed small dark hairs around my breast area and between my breasts and on my chest. What is wrong with me?