Confidence building?

I have a 6 year old who is playing in his first year of football. He plays in a K thru 2nd grade league. The league held a mandatory 3 day camp and then a draft. He was the first 1st grader taken in the draft and ability is not his problem. He performs well during drills and usually understands and does what coaches instruct him to do. The problem is that he has "melt downs" on a regular basis. He gets embarrassed easily and usually for no good reason. Yesterday during a back pedal drill he stumbled and fell on his butt and that was all it took for him to get embarrassed, freeze up and have to be carried off the field for 10 minutes or so. I've tried several ways to help him get over this with no success. I was wondering if anyone has had any experience with this or have any suggestions to help me break him of it and build his confidence up.

I should add the he WANTS to play and is not being forced into it by dad.