is he cheating on me???

[lazyboy]

Ok, i'm not themost confident of guys. I constantly suspect my boyfriend of cheating and a few days ago i thought i found damning evidence of this. first of all i must clarify that we haven't seen each other in a few weeks since i'm living in sweden and studying abroad this semester.
ok...so we kept in contact and we promised each other that if we were going to have sex with anyone whether intentional or not that we would inform each other and that we were allowed to do so as long as we informed each other about it
anyway, i asked him one day if he was seeing anyone while i was gone, he said that he hadn't. i didn't really believe him as he is a really horny guy who is known for being promiscuous and has had hundreds of one night stands-he is 35 by the way.
i created an account on gayder, jealously and proceeded to add a picture of an attractive guy from the internet on to the account. i messaged him and asked him how he was, what he was looking for (he replied that he was just going with the flow and not looking for anything in particular but was open tn things), i asked him when was the last time he had had sex and he said, not until last week, (bear in mind, i had left the country 3 weeks at this stage), i then revealed myself to be myself on the account and he said, that he knew it was either me or some other guy, that he only said that he had met someone a week ago to find out if it was me and knew i would reveal myself, that he thought it was suspicious that a new account with no views would message him out of the blue, and whatnot. he also said he expected me to do this for a while as i am an insecure and untrusting guy.
i want advice on this, was this excuse a good one, do you think i should trust him? i really don't know, feel free to bash me and my sneaking around, he did and said he was disappointed in me checking up on him and we seemed to patch things up but he has been a bit standoffish with me now, please someone tell me what u think of the whole situation.