Postpone the wedding plans and get into couples counseling.
Bottom line - if you do not trust him, then don't marry him. Simple as that.
Marriage won't fix a man. Remember that. It's not your job to train him, babysit him, be his Mommy, or monitor his phone/emails. If you cannot trust him from the get-go to know how to act like a real man, then you'd be an utter fool to marry him anyway.
Don't complain if you go forward with the marriage and then he's doing all sorts of shady shiiiit behind your back, because he's made you WELL aware of his personality before you've walked down the aisle to meet him. When someone shows you who he is, BELIEVE HIM. The first time.