Are my cramps from implantation? I am 4-5 DPO?

Husband and I have by ttc for 17 months. We had our first RE appointment last week on the day that I Od. I received my +OPK on CD20. We bd on CD17-20. I'm now at 4-5 dpo and have been having cramping all day. Do you think it could be implantation?