Period or implantation

Lisa

So I was about 4 days later with my period than what I thought I should have been and it was only 2 days. I typically have a 4 day period and have cramps and bleed quite a bit. This time I had cramping once and barely bled.. no I have a wicked headache for 2 days. Could that have been late implantation bleeding? It would have been 18 dpo. Or was it my period and I’m just reaching now?