Ex is suddenly ignoring me but we have a child together. What to do?

My ex and I have a 8 year old son together. A month ago my ex gave me the speech he doesn't want a relationship and can't commit to anything speech. He had been under extreme stress and I believe our relationship was one he could end so he could focus in the other stresses in his life.
He said he didn't know what the future holds etc but for now he wanted to be on his own but stay close friends.
My ex would contact me at least once a week to see how I am etc this lasted for approx 3 weeks then he asked if he could catch up in person.
I agreed as I missed him and our son had not seen him ( my ex had not asked to see him). When we met up his brother was there and was happy to see us etc.
my ex said all the right things and we ended up hooking up.
When we parted he said he would be in touch. I didn't hear from him for 3 days but was not worried as I knew he was busy and I was busy too.
In the 3rd day I was in an accident involving a semi truck and I messaged him to let him know about it. He ignored the message even thou he was active online.
The next day I sent him another message to say his Son and I are Ok in case he opened the message I sent the day prior.
My ex opened it and said he was glad we were ok and he was sorry.
I didn't ask him why he was sorry I just assumed it was because he hadn't opened my previous message.
I sent him a follow up message after he had replied to me to get no response again. That was a week ago.
I still love my ex and want our family back together but I am confused why he was first in contact and after we hooked up he is ignoring me?
Should I just walk away?
Is it likely he now doesn't know what to do since he ended the relationship and then was the one who made all the advances leading to us hooking up?
How do I handle the situation as we do have a son together and our son deserves to have his dad around but his dad is ignoring me? Oh I have never used our son as a tool and never would.
Thank you in advance
Ex is suddenly ignoring me but we have a child together. What to do?
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