How much should I expect?

I’m 6 weeks pregnant, our baby was planned but happened a lot sooner than we expected. The father of the child has decided he no longer wants to be with me but wants to be with his ex and their son. He only wants to go the the ultrasound where we find out the sex of the baby. But I want him to be involved in this pregnancy otherwise I plan on giving this baby my last name. But on another note, I don’t really know what I should expect from him. Am I looking at this wrong or what expectations should I have for him to be an active part of it vs just do what he wants?