In a nutshell, he's not being honest. Hubby is not respecting the rules/boundaries you two have and is thinking with the wrong head. It also sounds like a case of NRE (new relationship energy, if you're not familiar with the term).
You sound very committed to your relationship. The two of you need to sit down and figure out the WHY behind his transgressions. Though he's going about it in completely the wrong manner, my first instinct is that he has fallen for her. For better or worse.
I'm a pansexual female, married to and living with Indigo
(straight male), in a relationship with and living with Mr. A (straight, mono male).
One day I might stop "practicing" polyamory and just start living it!
Here Be Dragons
Originally Posted by AutumnalTone
Nobody gets a toaster oven for recruiting monos.