While approaching the airport to land the pilot was told by the unicom operator that runway 5 was active. He entered the pattern and while on final approach to runway 5, he encountered another aircraft landing on runway 23. He made a go-around and entered the pattern for another approach to runway 5. During landing he heard another aircraft report on final approach to runway 23. He did not see the other aircraft and became nervous about having a head on collision with this aircraft. In haste to exit the runway, he ran off the runway into the grass and the aircraft nosed over.