Originally Posted by
TrojanHorse
I don't think that's a skinny person problem, it sounds like something is amiss.
Coccydynia (inflammation of the tailbone) afflicts many people but one's weight is not a causal factor as it affects people of all sizes... I suffer from this because of a lower back injury and for me sitting in a soft chair is actually more uncomfortable than sitting on a well fitted bike saddle that gives much better support when sitting.
I would see one's physician to determine the causes for the pain as there are many other things that mimic this and cause the same kind of pain but require different treatment strategies.