I am going through exactly this problem at the moment. All I can say is, if you're also going through this difficulty of falling in love with someone outside the Church, first of all, don't hide this problem from your spiritual father. He can't help you if he doesn't know what's going on in your life. Secondly, while the rules are very strict (no marriage outside the Church), it's dangerous for those who are not spiritual fathers to throw the book at people in this situation and say "it's either the True Church or your true love". That is just as likely to drive the person away from the faith entirely as it is to persuade him to dump his sweetheart. It's better to marry inside the Church than outside it, but surely it's better to keep the faith and struggle to live an Orthodox life to the best of one's ability, even if one is barred from Communion, than to compound the uncanonical marriage by abandoning Orthodoxy entirely.
EDIT: Fr David Moser over at monachos had a very good post on this topic. Would I be allowed to reprint it here?