How do I bring this up...

(Backstory) I've recently started talking to a boy and he's so amazing! He's sweet as can be and super funny. He makes me very happy. We decided at the beginning of everything that we were going to take things slow since he's very new to physical stuff and I'm having issues trusting people after something that happened to me.

Well, we decided to go over to his house last night to hang out and he mentioned how he wanted to kiss me. A kiss lead to a few more kisses which turned into a makeout sesh.... a poor one at that. I won't necessarily go into detail but it was bad! He's only ever kissed one girl before me so I understand he's inexperienced but yikes!! How do I suggest better ways of kissing to him without making him think it was horrible?

Side note: it wasn't entirely awful, it just really wasn't good