my ex doesn't believe me

My now ex, does not believe me when I tell him I was a virgin before him. Apparently he thinks I was lying to him the whole time we had dated. I don't know what to do to convince him that I was a virgin before him, I hadn't messed around with anyone but one guy about a year ago before me and my now ex had dated. And the guy and I a year ago did not have sex. I don't know what to do about, and it really doesnt matter anymore but it just bothers me that my ex wouldn't/wont believe that I WAS a virgin before him.