What Causes Spotting With No Regular Menstrual Period?

The last maybe 5 months my period has been weird. the first 2 months i missed my period so i took a pregnency test it said negative. the 3rd month was blood only when i wiped for 2 days then maybe 1-2 weeks later the same thing happened in the same month. the 4th month blood only when i wiped and the this month the same thing happened. Normally when i have my period i get really bad cramps and dont want to move the past 5 months theres been no cramp only a pain in my stomech the size of a small fist.and it moves all over and its not all the time just if my stomech gets bumped or after im done eating sometimes when i wake up.