Why do you feel like you need to cry sometimes?

It's called sadness.

People feel sad for many reasons, usually because something sad is going on in their lives. If you've been feeling like crying for no reason, you might be depressed, which is what you call feeling sad without a good reason for the emotion. If you've been feeling like this for several weeks or months without knowing why you're sad, you should see a good psychiatrist to figure out what can be done to help you feel more like your old self again.