cheated on with call girls/escorts

Oh god what do i do? I have been with my partner for 11 years and we live together, I found out 2 years ago he had quite an infatuation with porn and asked him about it. He said he was doing nothing wrong and only looking and all blokes do it. I confided in a friend and she told me that there was nothing to worry about as her partner also did it but told me to keep an eye out. About 6 months later, I noticed that no mobile phone bills appeared to be coming in, i questioned him about it and he said there must be a problem with the company - mine were still arriving every month!! Alarm bells started ringing. I got a hold of his phone and found it to be full with names and numbers of these companies that advertise phone sex, text messages from them etc etc. I confronted him and he told me he was fascinated by it and did it for a laugh!! Stupid me told him never to do it again as it made me feel terrible and to me it was a form of cheating. Today, I have found out that this infatuation has gone further - he got a new phone and his old phone was lying on the bedside cabinet. I was mucking about more than anything but turned it on and still saved on the phones memory was messages from an escort giving her address IN THE TOWN WHERE WE STAY!!, costs and minimum length of appt. I am well and truly gutted that he has done this to me, I phoned him and asked him for an explanantion and he told me he was fascinated by the attention but was never going to meet her. I dont believe this, money has been going out of our bank account and he told me it was for tools for his work. He swears that he would never have sex with anyone else but likes the attention that he gets. i dont know what to believe anymore and need some guidance - i love him very much but he doesnt seem to realise the more he does these things the bigger the gap he is creating between us.