Implantation bleeding

I’ve read a lot of different things about implantation bleeding and I was wondering if you guys could help me out. I experienced some light bleeding 6 days after intercourse that was nothing like my usually very heavy periods. It only lasted a few days and I had pointed cramps in my lower right abdomen. Then I read that implantation bleeding happens at 4 weeks?! Very confused. My cycles are irregular so they are almost impossible to track but I’ve had lots of symptoms but no BFP.