Coccygodynia refers to pain in the tail bone when sitting and sometimes while standing. The problem is most common in women from trauma during childbirth. Other causes in men and women include trauma such as a fall at an early age. There have been some reports of sexual abuse linked to coccygodynia.
More serious diseases such as infections and tumors must be considered, too. A medical exam will rule out herniated disc, prostatitis, hemorrhoids, and cysts. Anal fissures are reported among the male homosexual community as a possible cause.
Even if your boyfriend won't discuss the problem with you, encourage him to see a medical doctor for a diagnosis and treatment. This is a treatable condition.