Marmie

a. Get an STD test to make sure you are safe - your health is first priority - never mind your husband on this one - just go do it for yourself
b. If you confronted him, made it clear he was causing you pain, and he refuses to stop - he's very likely addicted
c. Treat him like any expert advises you to treat an addict
d. Don't waste time dealing with him if he's not cooperating
e. Make it clear under no uncertain terms that him acting in any way that hurts will result in divorce

Consequences should shake him up a bit...

f. If you pay for the internet, cancel it
g. If you can control your internet router - lock it down - treat your home network like any other door on your home - you lock it up and keep the creeps out of your home
h. Make your spouse fully aware you won't tolerate this business in your home
i. Tell your husband if he is going to continue hurting you that he can leave

Remove any temptations from the home

j. check your phone bill for 1-900 calls
k. check your cc invoices for mysterious purchases

l. Collect all the evidence and be prepared to confront him with an ultimatum
m. Tell him he stops hurting you or he leaves the home