The love of his life?

Have hit a real low point today. It’s my daughters 5th birthday today, we bought a house on the weekend and I’ve come down with a virus. I also got a horrible period reminding me that I would of been beginning IVF medications. I don’t know what I’m doing, how I should be feeling or what I should be planning for. 
We’ve been looking to buy a house for a while now. We spoke, since finding out my husbands infidelity about upgrading our house to something we could afford to maintain if my husband was to leave which looks likely. Something that I was looking forward to so much has been tainted in the most horrible way. I’m so confused. He’s agreed to marriage counselling but I can’t help wonder if he’s just biding his time. I can’t cope with this anymore. I feel so sad. How can someone who was coupled with me just last year to have another baby all of a sudden decide that none of this is for him. He just wants to up and leave his wife and child. We haven’t been able to communicate effectively for a while now. Since having our daughter 5 years ago thing have been strained with us. We both don’t know if it’s too late to save it. He says that the affair was a symptom of our relationship breakdown not the cause. I just can’t erase all the hurtful things I read in those messages. I don’t know what to do. 
He says that both of them have broken off their affair saying that they both agreed that it was the worst thing either of them had done. No shit Sherlock that’s big of you. I wonder what the mood is like at work for them seeing that they work across the hall from each other. We haven’t really had anymore big talks since the night I confronted him. I dont think we are able to communicate effectively without a third party so I’m waiting till we go back to counselling to sort more stuff out. 
We discussed, among other things in counselling , my mum and her influence on our relationship. My mum is bi-polar and had been since I was young. She’s very needy of me and our roles are reversed in that I feel like the mother in our relationship. Whilst she helps me out with our daughter a lot and adores her she is very draining of my energy and she in turn affects my husband and daughter. It’s not as easy as putting distance between us as I’ve tried that and I find her neediness gets worse as she panics that she is being abandoned. 
So the counsellor suggested that I need to firstly emotionally remove myself from mum to give me emotional independence so that I can start working on our marriage. It feels like a lot that I have to do and not much that he has to, well at this stage anyway. 
In the meantime I can’t help but feel that our fate is sealed. That our 22 year relationship is being thrown out like waste. I don’t know where I am to go from here. I feel like I’m losing a limb, a part of my soul. No matter what our troubles in my heart I always believed that love was at the centre of us. He told me that night that I’m the love of his life and that he’d spend the rest of his life making it up to me for what he’s done.