What Causes Irregular Periods ? What Medication Can Treat It ?

Hi! im 25 years old married for 5 months now, since my menarche my menstrual cycle is irregular, sometimes i dont get my periods for 1-2 months and then its fine, and again after some months of normal monthly period this happens. whenever im not having my periods i take folic acid and i get them in a weeks time i guess, but sometimes even that doesnt help. 5 months back when i got married my periods just wont stop,(i took dicyanone to stop them but started having clotted blood ) then i started taking primolut-N for 21 days and then i had the reversal effect that is having my period, till 3 months i had em normal like every month, but now again i lost my periods for a month now, im taking multivitamins but i just dont know what to do. I even got the pregnancy strip which came out to be negative as i was sure it would!! Please help me docs!! i dont know if my cycles are ovulatory or what!!!!