Based on the history given you seem to be suffering from coccydynia
Most of the time its exact cause is not known. However it may develop due to childbirth, an injury or accident, such as a fall, repeated or prolonged strain on the coccyx (tailbone), poor posture, being overweight
It can also be due a bony growth on the coccyx, the coccyx being too flexible or too rigid, and arthritis.
Since your symptoms are lasting for about 3 months I would advise physiotherapy
exercises, massage and stretching.
Avoid prolong sitting and use specially designed coccyx cushion ('doughnut cushions'). Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen can also be useful.
Hope I have answered your query. Let me know if I can assist you further.
Dr. Mohammed Taher Ali, General & Family Physician