I’m not sure what to do

So.. I’ve been having sex with my high school friend (were in college now) and yeah we’re talking and dating, but he’s never had a girlfriend, he’s had sex twice before me and honestly, the sex isn’t great. And I want to tell him something I just don’t know how, the way he moans is a turn off and i honestly just don’t feel the chemistry in bed. I like him a lot, he makes me happy. Just not in bed.