Why do my parents not understand I get stressed easily?

Parents, let alone anyone else can never fully understand what you're going through - only you know truly. Don't be scared and stressed that they don't understand because all they really are doing is caring and worrying about you. The reason they do this is that they love you. Try your best to focus on your feelings and emotions first before getting into another stressor. What you can try is giving detailed examples and really let your emotions follow through when you talk to them so they empathize with you. Even though some parents may not comprehend how easily you can be stressed, just know that you should focus on your stress first.