Needless to say, I sense a major insecurity problem. He seemed to enjoy your cock and expressed it physically and verbally. Yet you still seriously doubt yourself merely because your dick is slightly thinner than average (but WAY longer I might add).

Based on your description it looked like you fucked the hell out of him and he loved it. Yes there is a chance that he was faking it all just to stoke your ego in regards to your insecurity over your somewhat thin dick. But, unless you see some concrete evidence of deceit, don't be a self doubter. It isn't good for the soul.

You stepped up to the plate as a man and acquitted yourself well, yet you are full of self doubt. Just don't go down that road. You don't get to be a good lover by convincing yourself you aren't. Be proud of what you (and your cock) did for him.