I know I am angry, I can feel it and often show it. Why do I still have pain?

Buried sadness. People who are sad and express as anger or bury this internally as depression.
Consider. I am not clear on your pain. It has been well proven that mood and pain are closely related. Mood can worsen pain and pain can worsen mood causing severe depression and agitation. If this is what you are talking about, I recommend you have both issues addressed by your primary care provider sooner than later. Good luck.