What Causes Irregular Periods With Spotting?

i havent had a regular period since i started having periods and i stoped having them after about 2yrs of having them irregularly and then i got a 3month supply of birth control and that worked and then when i ran out i stopped having them. i had a pap test and it came back normal. and then last month and this month i noticed that i would bleed a little when i would pee but it only last like 3 days. what could this be?