embarrassing bathroom problem

I am a male college student. I don't know for sure if I have a medical issue but I do have a problem I want to find out about. For some reason I seem to have unusually large bowel movements. Sometimes it is even enough to plug up a toilet. They are typically 20-25 inches long and 1.5 to 2 inches in diameter. It is very hard to find information about this but this seems to be a lot bigger than average. My B/Ms are not hard like constipation at all. I go once every 2 to 3 days. I did have a couple of periods of constipation when I was 5 or 6 years old but I don't feel like that is related to this. The first time I noticed this problem was when I was 12. I would like to know what the normal size is and if there could be any medical problem here and also if anything can be done. I don't normally have any problem but sometimes it has been very embarrassing.