Back story: I’m home for the summer and I’ve been having sex with an ex from 3yrs ago (I broke up with him) I’ve slept with 4 guys since him but he hasnt slept with anyone and I recently found out that he still has feels for me

Help: I’m staying at his house Thursday because we have off work and I want to like blow him away in bed but like not give him the idea that we should get back together.... how do I do that? In other words what kinda sex is we’re just fwb sex?