I’m glad you’re already doing step 1 and getting professional help. Also, a second opinion can also be helpful.
I think step 2 should be no sex whatsoever, and comprehensive suite of STD tests. No matter how much you still love him, no-one should risk their own health.
If he has had an affair before, plus he is currently lying about this one (do you RELLY believe it isn’t physical?)… there’s probably been others too.
I can’t recommend highly enough that you stop having sex to protect your health and get tested immediately.
