My son is 3 yr and 3 mnths old and has speech delay and can`t express himself,what could I do for his problem?

Seems like you are doing it. The only thing I can think of is maybe just sing with him something with simple words maybe just the ABCs. He sound like he might need a child psychologist to work with him if he saw some abuse. I don't know you exact situation but if he think your ex hit you because you talked back or something he might be afraid to talk because he might get in trouble.