This condition is called coccydynia. I have experience in handling these kind of problem.. You won't get this method of treatment with traditional Physio practitioner unless they identify the cause for this problem... During consultation I can explain you those...it is a chain reaction from one problem to other like you said about your foot pain..using a donut pillow is just a temporary solution through which you can sit comfortably but you have to correct the affected muscles...pls contact us @ www.myokare.com...