So sorry to hear that rue, unfortunately sometimes our feelings are not returned equally. When i'm considering breaking up with someone, I often ask myself one question,"am I happier with this person or am I happier without this person?" maybe it was too intense, especially for younger couples, there's one who may feel pressured or controlled and wants to just be young and free.
To stay depression free, i'd recommend the old saying,"living well is the best revenge", that is, go out, have fun with friends, meet new people and have a grand old time!------you heard about the "replacement"....He'll hear about your fun. :)