I don't know much about your situation but from what little you've written the love you're describing seems less like metta than it does sensual desire and infatuation. I can't pretend to know, however, so please don't take offense but you should seriously ask yourself if the desire to be with this girl would be the same if she were an old hag (which she will be some day if she's lucky) or if she decided to fall out of love with you. Would you still want to be in love and spend lifetimes with a person who didn't feel the same. I wish you all the best and hope that you find all the happiness a lay life well lived can confer upon a person but do proceed with care and don't believe everything you feel without taking it to task. Be well.
To avoid all evil, to cultivate good, and to cleanse one's mind — this is the teaching of the Buddhas.
Uposatha Observance Club:
My Practice Blog: