Over the years there have been threads from posters so upset because their partners are ANGRY that they haven't "got over" the affair and "are still thinking about it".
So angry and nasty because, unlike them that have moved on, the cheated on partner is still upset.
Other posters often write they regret taking them back and eventually divorced, as the relationship was irretrievably broken.
So not only are they unfaithful they were also bullys who thought THEY get to CHEAT and decide how long YOU are allowed to be upset about it.
At this point OP, I really think you need to stop thinking about what HE has done and focus totally on YOU and the type of woman YOU are and what YOU want.
Are you the sort who can move on from this with him and just forget all of the nastiness and deceit?
That's what this comes down to.
Either way you have healing to do.
Do you want to re-commit your future to someone who despises you, and was 100% ready to dump you and your son when a more appealing option came his way?
That is your choice IMO.
Take him back, suck it up and hope to God that no one else EVER catches his eye.
OR
You realise, NOPE, I am not placing my future happiness in the hands of a man who felt comfortable enough to tell me he despised me, wasn't happy, cheated on me and only came back when his EXIT plans went tits up.
This is about deciding who YOU are and what YOU want and what YOU will accept.
We teach people how to treat us.
What do you want this to have taught him about how he can and has treated you?
What you decide will be what you will teaching him.
I think you sound like you are worth 10 of him.
He didn't only cheat on you, he cheated on your child, you don't ever want to forget that IMO.
Actions have consequences is what he deserves to be taught, and you are not a plaything to be used, discarded and picked up again because you have further use after all.