hugs, Bugsy, sorry to hear it's not getting better. Wise words from many people below. I think Jimjams and Crunchie are right about taking it slowly - it's so tempting when things go wrong to react quickly but I absolutely think you are right to feel your way to what you want in your heart.
One thing that did strike me was that originally you had said you'd worked hard at making his life easy and being a good partner - was this effectively shielding him from difficulties and your emotions? Are you still sort of doing this now?
It's really important that he realises what you really mean by changing - it may be changing his job, it may mean blocking this woman's phone number from his mobile, it may mean telling his boss he can't travel for a bit, it may mean treating you like a queen, whatever you need to feel secure. It sounds like he's just carrying on as normal and waiting for you to come round, which isn't acceptable in anyone's book, but may be the way he's always used to relating to you. He needs to understand you need him to be proactive, in whatever way helps you best.
If you find it hard to tell him this, even at counselling (although a session on your own might help), then have you considered doing it in writing. I'm tempted to suggest you start texting him with how you feel ('I wish I could trust you' 'I need flowers' 'My day is crap, I need cheering up', whatever it takes), it would certainly be a way of starting a dialogue and reclaiming texts from that awful woman. And if it does work out for you in the long run, it might be the start of you being able to express your need for mutual support better.
You know we're here for you if you need us.