Yeah, it's probably a luberication problem, thanks !
I don't know whether it would be from your implantation.
It may be simply that he is entering you from a different angle, and you may not be lubricated or he may not be lubricated enough to enter you. He may just have to be more slow and gentle as he enters you and not push down to stretch the part that does not stretch too well.
If it hurts, you must tell him to change position.
Book an appointment to see your doctor or a gynaecologist.