Why do you think your tailbone (coccyx) is broken? Did you fall on it recently?
If you have been experienceing this severe pain since you fell then you must go to the doctor and have an x-ray taken to determine the cause of the pain. Usually, if a coccyx is broken, the pain will go away after about 6-8 weeks, on it's own. Sitting on a rubber ring helps to take pressure off of the coccyx area. It sounds like you have injured more than your coccyx and an x-ray is required at this time.
Has the doctor told you that your pelvic fracture is related to your coccyx pain? Has your doctor suggested any particular reason for your tailbone and leg pain. You need to be examined and treated by an orthopedist or a chiropractor for diagnosis and treatment. Further investigation studies need to be done on you.
Oftentimes a pelvi fracture is accompanied by pain in the pelvic region, and usually occurs due to trauma. The pain that you describe can be related to sciatic nerve pain, which is very painful in the lower back and radiating down the leg. It resolves with time. Ibuprofen can be taken to relieve pain. Your pain can can be a result of damage to a disc in your lower back. An orthopedist is the specialist who would investigate this for you. In the meantime, a chiropractor can provide some pain relief as well.