He probably guessed that I am once again very sexually active so it could be a jealousy thing ?
Probably. He thinks, 'she didn't want me, how come he's getting it from her ?'
It dents his ego that, in his view, you want your new man over him.
He's pretty much sulking and thinking, 'so you don't want sex with me but you do want sex with him.' What's that about ?
He probably does have some residual sense of ownership over you/your sexual desire. That's what his problem is.
Your kids get along with him as well.
He just can't fathom what's going on. What it's all about. I mean if he'd have got that level of compliance from you, he wouldn't have left. You would all be one happy family which suited his convenience.
You've gone and confused him now. Tea hee !
It's going his brain in that you're having sex with some one else but not him. Y'know, cause no means no.