I would use caution when making any major announcement in counseling sessions.

Generally you want these to be relatively safe places. If he is blind sided in a session - the likelyhood of him wanting to go back I think will be gone.

Make an appointment for counseling - come clean before the appointment. Let your husband know that you know it is a problem and that you set up a counseling session for the two of you to discuss it with professional help.

If he is anyway abusive then please ignore this advice...