I am really miserable right now. My fiance does not believe in infidelity and I know he has never had an affair (because since we've been together we have spent most of our time together... but also because I do not believe he would). But this will not always be the case, in fact in the future I know that we both want jobs which will take us apart from one another for longer periods of time (business trips, training etc). The problem I am having is that whenever he thinks I am asleep he goes online and does things (Im a light sleeper and he always wakes me up even though he is quiet). He looks at pictures of girls he knows on myspace and then watches porn and masterbates (and these are girls that are not as good looking as me so I don't get it), he goes on Russian escort sites, looks at pics in Craigslist classifieds etc.

When he does this I get so worried and all these things cross my mind. 'He's only with me for my looks. He's only with me because we share this or that. He wants to cheat. He wants other women.' etc.

We have an active sex life, we talk all the time (not about our feelings, I mean just talk in general about our passions like politics and history), I know he wants to spend the rest of his life with me. But if he is fantasizing about other women now (which he says he isn't but I don't believe him because why else would he look) when we are together, how can I trust that he will not cheat when we are apart?