If you cry too much is something mentally wrong with you?

You could turn that around, and say do you have a mental illness if you cry too little.
The way I see it, you're best to be somewhere in the middle, crying occassionally, when you need to, and not holding everything in. But then, everyone is different.

The only time I would personally think something was wrong with a person would be if they broke down crying over nothing but, I'm no psychologist.

No.

Crying lets all the anger out.  If you cry over something that somebody has done to you, everyday crying then you should see a therapist.