One side of coccyx is hurting come n go pain when i bend over.. what can it be? pain is not everytime i bend over

Depends on: How long this has been going on, previous history of trauma, and associated symptoms, or lack thereof, your diagnosis will require to see a doctor and in some instances, an x ray. So not knowing the particulars makes it difficult to give you a better answer than that.

Family practice: You probably hurt it somehow. The muscles may have been stretched and with certain movement it becomes irritated. If you fell on it there may be a fracture.