It happens often, and youre not selfish for wanting a certain type of love, its just that not very many people can give it.
With my last girlfriend, I found out that there are different types of love. there is the love I gave her, something that forces me to make unnessicary sacrafices for her wellbeing because the only thing In the world I care about is making her happy. I call this love obsession.
Then there is the love she gave me, a force of attraction that caused her to want to be near me. she wanted to do things with me and enjoy my hobbies and laugh at my jokes because she liked the look of my smile, but she still held her own wellbeing above mine. when she discovered she had this love for another man as well, she tried to date us both at once. I call this love fascination.
The love called fascination is real, but it is selfish. Obsession is selfless. A person who is obsessed will continue to love a person who is fascinated, even long after she cheated on him, because she is still happy around him, and he still cares about her happiness more than his own.