How old is he?
Five years isn't that much. There should be no reason for him to be uncomfortable. There are lots of couples with big age gaps.
5 years seems a lot at both your ages, however in the big picture, it's nothing. You're both consenting adults and I doubt he's much maturer mentally than you.
Ahh are you serious? I thought the age gap was a lot bigger. I dated someone 18 years older than me! He viewed me as his "little sister" WTF! You're okay!! He's dumb.