That can happen.
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.