Communication is very much at the heart of any relationship and it is often a problem with 'long-distance relationships'. You are obviously worried about a breakdown in the communication between you and are worried as to the reason for it. It is always possible that there is a simple explanation, rather than any sinister or devious reason you might be thinking about. You need, though, to know why there has been this breakdown. You need to try to take charge of the situation. The only way, it seems, that you can do this, is to send him another email asking him if everything is okay you are worried because you haven't heard from him. Try to make sure your email is non-threatening to him and doesn't make suggestions of forgetfulness, lack of love, or infidelity etc.