Any help

After a 6 years relationship 
I find out my husband was cheating on me  
We have a 4 years old daughter  
I s been only 3 weeks since this happen is been really difficult for me to get it off my mind 
Any recommendation of what kind I do what can help 
I was thinkin maybe therapy could help me and also for me to be a better mom to be available handle when my child ask for its father