“Irregular Periods”

I have had 3 periods this month. I have no pain other than my usual cramps. i took 3 pregnancy tests they all came back negative. im only 22 so i dont think it is menopause. i was on the depo shot when i was 18-19 but ive been off of it since. i had no period for 1 year after i stopped the shot and now my periods are very irregular and i dont know what could be wrong.