He wasn’t ready, and ended things abruptly

Was dating a man for a couple of months now and things were going really well. We’ve been on several dates and I felt I could really laugh with this man, there’s no awkwardness and we always have a good time. He sent really lovely texts in the mornings and has recently been saying things like how he’s excited for us to do things when places open again, and how he feels really happy. I’ve felt really comfortable and happy with the pace and I do believe he is really into me. From the beginning, we have both been clear we both want a relationship, and I’ve been developing feelings.

Last week, I met a few of his friends for a socially distant picnic. He was saying about how excited he is to introduce me to them as he thinks I would fit in perfectly. And I had a really nice time!
We had plans to meet on Sunday and he texted me in the morning saying he couldn’t wait to see me 🥰

We met up and I instantly knew he was completely different. He seemed very quiet, down and a bit funny with me. But we went on our walk and to grab a bite to eat and I had a nice time with him. He was being off but was still holding my hand, giving me hugs etc. I excitedly gave him some ideas of what we could do next weekend and he agreed to them all. We also went to the shop to buy some drinks for the evening.

Later in the day, I ask if everything is okay as he was being really unresponsive. He says “yes, absolutely, nothing at all”. Then, out of nowhere he comes out with “I’m not ready for anything”. Of course I was shocked and reacted to this, saying he was acting like he was ready, said all these things to me and has basically gone from 100 to 0.

He said he isn’t over his ex. He was with her for 5 years and they only broke up a few months before speaking to me, and it was messy. Me being at the picnic just made him think of her doing all those things, and he thought he was but he isn’t ready for anyone to fill that gap – he was adamant it was nothing to do with me.
He seemed so unsure about things and it was all so sudden, he said some contradictory things, and said his “head was f**ked” and he seemed very anxious.
He decided in the end that he is not ready to even speak to/text me or anyone.

This has been so hard for me to hear and the biggest shock, especially as it seemed to be him pushing towards a relationship and, a matter of days ago, telling me he’d never been so happy, he sees me in his future and he can’t wait to get to know me even better.

The thing is, I fully believe him. He was very teary as I left and said he was disappointed in himself, as he liked me so much, but knows he needs time for himself. He seemed so unsure about everything he was saying but we said goodbye and now I am devastated.

4 days on and it still feels weird going from so much to never hearing from someone again and I’m finding it hard to adjust to him not calling. It’s such a sad situation as I feel we’re so good together and he thinks so too?? What do I do?