Are you a survivor of sexual, physical, emotional abuse?
Are you a soldier returning from a war zone?
Have you experienced any other kind of trauma in childhood, or even later on in life?

PTSD is defined as a person being exposed to, experiencing, witnessing or having been confronted with an event, or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others. The person's response involved intense fear, helplessness, or horror. In children it may be expressed by disorganized or agitated behavior.

Trauma, generally, is subjectively felt by the person, that is, only you can judge if you were traumatized. One person's manageably painful experience can be another's trauma.