What Causes Irregular Menstrual Cycle?

hello well i have had nausea for 4 months nowa have nt vomited been put on antiacidpills not helping at all and i havent had my period in 2 months almost 3 what does this mean i have not had intercourse so hopefully thats out of qeustion but i also go less fregeuntly i go pee once a day or even once in 48 hours plz tell me whats wrong