Its easy to become lost in a relationship, especially if you've only had a few and it feels like this is the only one you'll ever have. I know the pain well and only gentleness with yourself and time will begin to ease the sadness and feelings of loss. Mostly you are probably feeling a lot of rejection and that no one will ever feel the same about you again. Its true that the person you love has a unique way of caring about you and no one else can give you the feelings just the same as you've had with this girl but try and remember the world is full of people also searching for someone else and in time your paths will cross. Try not to give up on love but ask yourself some really serious questions about how to be in a relationship and not take too much from it while still putting in enough to keep it going. This from a happily single person who is not in a relationship at all right now. Maybe focus on your own happiness first to the degree that you are filled with the life and energy someone else would like to be a part of. So sorry about your dad