I'm sorry, that really didn't go over very well. At least your mom seems a bit more understanding. Just give it time. Your dad will calm down. They may not have reacted ideally but they are ultimately concerned for you and your health. People tend to freak out when they find out a loved one self harms because self harm is so misunderstood. Maybe you could show them a website about self harm or write them a letter so they can understand what you're going through better. I'd recommend you show them this
(click here), it's quite informative.