You know him best, but generally it’s bound to be embarrassing. And since it’s supposed to be something he’s doing secretly he’s bound to be defensive and possibly angry about it, making your dishonesty at looking at his phone the major issue, as major an issue as you feeling he is betraying you by using porn. Somehow you both need to discuss the issue sensibly like adults and as husband and wife, love is the key to that maybe.
There is a need underlying the habit he may have developed. The porn should stop at least and ideally you should be approaching each other for your needs. That means you both need to be available to each other in that way. How you deal with that aspect is your call and can’t really be described specifically because it’s unique to some extent.
By using porn he is making sex become an insidious thing, the urge to have sex is not insidious in itself. I would avoid blaming him as such, just out of compassion for his well being and spiritual self he needs to be helped to see that he should desist using porn, that is a separate issue to satisfying the underlying urge which he can’t be blamed for having, though he needs to control it and you can help him in that way.
These are just my thoughts on the matter, you should see a therapist again perhaps, I’m certainly not one myself.