I need help

I have been spotting for 3 days now on and off. It’s very very light. It’s not my period because I never spot before my period and if I do not this long or light. I have very heavy and painful periods so I can tell. Today I noticed a little bit of cramping. Off and on as well. I have been taking pregnancy tests and they are negative, and I googled it and seems like it could be implantation bleeding. How long should I wait to test? It’s been going on for 3 days. I don’t know when I ovulate because I have irregular periods. Should I call the doctor? Or wait longer to test again? What do I do?