Does depression cause pain? if so, why does it cause pain? what's causing the pain?

Highly likely: Pain is perceived and tolerated differently by everyone. Chronic pain will undoubtedly lead most to experience depressive symptomatolgy, although not all will meet criteria for a frank major depressive episode. Acute pain is less likely to cause mood fluctuations. Those with a history of severe depression often describe having psychomotor slowing/fatigue and maybe even generalized pain.