Where's the empathy?

I'm lacking empathy these past few weeks. It's hard for me to take in so many people's issues. I've even found myself literally walking away or changing the subject when someone is talking about something that is going on in their life if it isn't something postive. I just can't take it. Maybe it's because I don't know the right words to say? It just seems like if it's not one thing it's another. Things are going okay in my life, so maybe I'm just trying to avoid letting other people's problems take a toll on me.