Irregular Periods?

Hey I was just wondering what's considered irregular periods because my period sometimes comes 2 weeks after they just finished or almost a month & a half late & sometimes they go from 5 days which is normally the average for me to 8+ days or 3 days long periods I heard birth control can help with this but I'm not sure if I'm classified as having irregular periods & if birth control actually works please help thanks. 😊