My boyfriend called yesterday and ended our relationship and I don't know why?

We have been together properly for around 8 months and things have been going great (previously we were friends when he was still married but when that ended he said he wanted us to be in a relationship, we both did. He is my soulmate and was also my best friend. Anyway, he was going to apply for a divorce today but discovered on Saturday that his ex had already done it all and the papers are being signed next week. (he left her). Things have been going great between us and he had recently made so ace in his house for my young son to stay too and that he wants him to know can be at home in his house. Only yesterday we were making further plans for our holidays things we needed to get, spending money etc. We are booked to go on a US road trip in September from Scotland, me, him and my son. And he has been really attentive of late. We have let everyone know of our relationship etc and he just kept making plans. He is 42 and I am 32. Last night I told him I had a nightmare that he ended it with me and went back to his ex, he reasssured me that we wouldn't end etc. He left for work this morning, we had even slept together. All night he cuddled me as he has being doing more often lately. I text him a couple of hours ago to see if he was getting a week off to go camping next month as we had only talked about yesterdays and he said to me "answer ur phone, I need to talk to u" so I called him and he said "sorry, shouldn't do this over the phone but it's not working, I don't want a relationship and u won't change my mind. I said where has this come from and he said he'd had doubts in the last couple of weeks and that he wasn't happy (I have no idea where that came from). He said we will talk when he comes down on Wednesday as normal. I'm confused. Is he just scared or what is going on. He said don't cancel your holiday, just go u and ur son. He said I'd like to be friends still. Is he just feeling like this because he discovered his divorce will be finalised next week and he