Suggest Treatment For Irregular Menstruation

Hello I am 20 and currently have a mentrual cycle of less than 28 days. For 5 years my periods were fairly irregular, sometimes with long gaps between two. (I assumed this was quite normal for the first years) However, recently (past 12 months) I am having shorter gaps between periods, the cycle sometimes being, for example, 20 days. Is this something I should be worried about? Any answer will be appreciated. many Thanks