If it wasn't 'cheating', he'd be doing it with you at his side. No he's hiding relationships from you, yes it's dishonest and what I'd call 'cheating' .
You know this, of course.
Hope the counseling helps, but he does have a history of 'repeat offenses', doesn't he.
Oh, don't bother blocking the numbers - if he wants to make contact, he'll find a way.