I need advice please.

My boyfriend and I have been together for a while we are very close we met in cosmotogly school and I graduated before him but there was this girl there and her and I didn't get along after a while. But they became friends . After months went on we started to have problems then he has told me he has developed feelings for her that's I took it and now a month later it's just a feeling as a friend is it okay to care about somebody that's not me I just don't know how to deal with it .