How can I convince him I didn't cheat?

Ok…. This happened last Saturday night… We had friends over… yes we were drinking, But it was getting late and I was pretty buzzed up.. My man had left to the store with some friends to get more beer.. I stayed , so I figure I better go to sleep before I get too blank out.. But anyways I had recently put my clothes in the other room closet because I have a lot if clothes more room, but I went in our room took my pants off and remember that I had out my clothes in the other room… Soo I figure I run in the other room to get my shorts before they get back.. but to let you know they were some friends in the living room watching tv so I ran across, couldn’t find them just when I ran I walked back my boyfriend came in and saw me with no pants, So I ran in the room to put pants on…. So he thinks that was pretty weird to see your girlfriend with no pants.. I told him the story but he just does not believe me… I have always been honest in our relationship … I have no idea what to tell him but he just does not believe me… we have been together for 8yrs and going on 9 years… what should I says to him for him to believe me..????