don't hold in the tears. As painful as it may seem, crying can actually help you to express yourself, and can relieve some of that burden that you're carrying around.
Go easy on yourself, and when you feel the need to hurt yourself, try doing something else. Distraction is the best method (for me anyways), even if it's only for a brief period of time. The important thing is to interrupt that negative thinking cycle that makes you want to hurt yourself.
Try and take care, ok?