I'm sorry you're having such a rough time.

What a crappy situation.
Have you seen an attorney yet? It sounds to me like you'd really like to have your husband come home. But I don't think it would hurt for you to know what your options are. You may need to protect yourself financially.
I have to be honest, if I were me, I'd be done with him by now. And I'd be a might bit vindictive about it too.
I'd be finding out if I could sue the OW for 'alienation of affection', and my husband for adultery. I'd be asking how I could get the absolute largest settlement possible from both of them, so they'd never cash another paycheck without thinking of me.
But that's just me. You're you and even if you aren't interested in divorce at this point, you can still educate yourself on how to best proceed now, so that you'll be in a better position later. If it comes to that.
In the meantime, try to get out of the house and do some things that you enjoy. Visit with friends, get involved with some new hobbies. Whatever keeps you busy. It's not good for your body to dwell in sadness. It can make you literally sick. So hang in there, and do your best to take care of you. Your kids need you to do that.