Your words suggest that you have had a very strong reaction to his actions. It was this sort of reaction, i suspect, that he hoped to avoid; this could be why he lied to you.

It is no wonder that you feel uneasy. It is quite difficult for me to believe that his barber texts him multiple times in a week about his haircut. If she is "goofy", perhaps he would be willing to share those texts with you.

And he still sees her monthly for a haircut?

It will be hard to forgive when you don't know how close they became and therefore what you would be forgiving him for and to what extent he betrayed you.