in 2015 the woman my H had a relationship with started to follow me via twitter. I contacted her and I said if you want my H I can give you his number, She then went on to say she didn't need his number, they'd been seeing each other for 6 years. My H took 2 days to get back home, proceeded to say he'd lived with her for a year in Belgium. After a few months he then said it was 18 months. I've no idea what the truth is.
Yes you do. The truth is he had a relationship with this woman for 6 years. Odds are he's still having a relationship with her - have you checked with her? He's lying to you and you know it.
As for saving the marriage - do you know WHY you want to save it? From what you've told us, he's been an absentee partner your whole marriage almost. I'd be willing to bet there were other affairs in the past. And when you begged and grovelled for a year for him to take you back - he KNEW THE WHOLE TIME that HE was a cheater and yet he let you go through that.
It doesn't seem like he's made any sincere effort to repair the relationship. AS long as you pursue him, he won't. If you move forward with your life, he MIGHT - or he might not. Sometimes when they realize they're about to lose you, they snap out of it. But I'd place those odds lower with your H, as it seems he checked out of this marriage decades ago.
I'm not suggesting you go out and date. In fact, I recommend against that until you're well out of the relationship, if that's where it ends up. But I DO recommend you start going out and getting a life, doing fun things with friends, take up new exciting hobbies, be a little mysterious. Let him WONDER if you're moving on without him. And live your life for YOU. Figure out what dreams you've put on hold because of him and child-rearing and pursue them.
Right now he has never really had to feel the loss of your companionship. Let him feel that loss. Create a new and exciting life for yourself, aligned with YOUR values. IF he's capable of recognizing your value, he'll work to become a man worthy of joining you on this new adventure. If he's NOT capable, you'll be that much further along in your new life and that much closer to a new relationship with someone who truly values you.