Do all men sleep with prostitues and cheat?

I have been dating my fiance for 2 years, but when we first started dating something happened that I can't get off my mind - I was using his computer, and was downloading some images, when I came accross some images of naked women that had been stored in the history of his computer i.e. he had been looking at these women and the computer had put this data in the computer history. I looked closer at the pics and realized they were not , but rather were images from a website with prostitutes. When he came home I asked him what was going on - and he said that he had organized a bachalor party for his friend and was in charge of finding the stripper, and that often his friends would hire prostitutes to strip rather than strippers because prostitutes come alone whereas strippers come with a bouncer...and ured me that nothing had happened...I am not sure what to do really - I think I trust him, but can't seem to get past this incident and it is making me ill...Will I be like this with anyone I am with? Or is it the relationship? He is supposed to have a bacholor party and the thought of it is making me sick...what shall I do? And how do I know he was looking at that website for a party, rather than for himself? Thanks...