I lost my ability to feel empathy?

I used to care about other people's problems I did volunteer work at a point now for the past 3 years I can't stand any friends, family or anyone that gets emotional or expresses their problems, its annoying. I feel bad I try to make an effort to make it seem like I care but they can see right through me and call me on how much I don't give a crap about anything. I really do try but its so brutal and painful to do so.