Has he said recently (in the past several weeks or days) when you have spoken to him that?
he cant help his self from flirting and he really didnt think it was that bad
Has he yet to come to an understanding of your hurt and pain.?
When the feeling of it "comes back" do you notice certain triggers? My wife's trigger was the "time of year" when it happened (around Thanksgiving). It could be a piece of clothing he was wearing when you found out...it could be the physical phone...any receipt laying around, etc. Notice and understand these triggers so you can deal with this easier. No, its not going to be easy for awhile. Only when your husband seeks your understanding through active listening will he begin to change.
There is no rationalization to the want to have other people of the opposite sex make a person feel "special with butterflies" again like when first dating. Does it make a person feel good...SURE IT DOES. But it can only damage a relationship whether male or female if the road of desire and deceipt is followed. Like I said, no matter whether a person is male of female (I am combating this in my marriage with a wife who is going through a mid-life crisis/transition...see my communication post -
http://www.secretsofmarriedmen.com/phpBB2/viewtopic.php?t=360) what they seek will not last and is very damaging to the marriage. The uplifting of the marriage and trying to make the marriage "butterflyish" should be paramount not seeking it from outside the marriage. It takes a consistent effort of love and actions for the person that is causing the break of trust to show the issues are in the past and will not happen again. If you dont feel the actions are consistent, then the mending cannot commence.
Like BushBabie said, there will be alot of arguing and certainly anger but he has to understand. Try to keep your cool and intelligently discuss your disappointments and difficulties in restoring unity. Whatever your faith and religious beliefs are, lean on them. I have and its made a big difference in my life to understand my wife and to serve her (and take that as easy as recognizing her needs...glass of diet coke, cup of soup, backrub, making sure her car is filled with fuel, bringing dinner to her work).
Ultimately your husband needs to understand your hurt that he disrepected the marriage. Until he does and puts himself in your shoes and realizes what it would be like, all he will do is rationalize his behavior. I dont know what else can persuade him if he has downplayed marriage counseling, religious guidance, books like Dr. Haltzman's...most people that I have heard of when they are troubled, are seeking the help by themselves. It is only on imminent disaster that the other person in the marriage will finally see it takes both husband and wife to make it all work. Good luck, and God Bless you both.