Suggest Treatment For Irregular Menstruation

hi ok so i am really irregular with my period and sometimes i dont get it for 3 months at a time im 18 and i the last couple of months ive been getting my periods really frequently i got mine on the 4th and just now on the 27th wtf? my boyfriend fingered me and popped my cherry recently but i have never had intercourse with anybody EVER whats wrong with me i am not on any medication or birth control