You can call mental illness many different things, and it can have a variety of causes. There may be a genetic predisposition to certain kinds of dysfunction, that some people have the resilience (learned and/or genetic) to overcome, while others need more help. Stress brings out anything that you may be struggling with, and makes it harder to cope. If you have concerns that interfere with your ability to live your life in a satisfactory way, then I would encourage you to talk to a therapist about it. It doesn't so much matter what they call it, but if you are having trouble there will be a category somewhere in the DSM-IV that will fit close enough (if you have to have a diagnosis to get help), and you can probably benefit from talking to someone about your concerns.