My ex

I have been together with my husband for 10 years now, Me and my ex keep in touch. Although as I am learning about myself through scholars is that the reason I do that is because for some reason I feel a bit scared of him.
He text me this morning saying he haven’t heard from me for a while. It had been a month which isn’t totally unusual. But he was the one that reached out then too. We can go 3 months without being in touch.
I have been replying to his texts but not reaching out on my own.
If he asks to meet for coffee pre-pandemic I would go, partly out of fear something bad would happen if I didn’t and partly because I do like him as a friend.
I have no idea why I am scared of him..but I feel like I have to keep him happy and the way to do that is to stay a bit in touch.
He has dated lots of people since we stopped dating and the reason we stopped was because I wanted to meet someone to share my life with and get married and he didn’t want that, with me or with anyone.

C. Ex texted.
T I need to reply quickly to keep him happy
F. fear.
Actions. I reply quickly. I keep checking my phone to see if he replied.
Result. I am still in a type of relationship with him.

I would like to break out of this cycle using the model could you help me ?

Thank you