I think you are stuck in a rut. You are not happy. You don't trust him, being with him makes you anxious and snooping has become an obsession to the point that you are hoping you will find proof because deep down you know there is more to all this than what he has admitted.
If you do find what you are looking for, what then? Is it proof that your not crazy? You don't need it. You are NOT crazy. He is shady and you need to stop this vicious, dysfunctional circle and LEAVE!
I know its hard after so long together but do you want to live like this for the rest of your life? And it is only