I read an interesting article on post-op bleeding after tonsillectomy today. The premise of the article was to determine how much bleeding was acceptable after a tonsillectomy. The hospital I work for recommends coming to the ER if you have any bright red bleeding from the tonsil beds. The reason being that there is a major artery that is in close proximity to the operative site.
After reading the article I still agree with them. If you don't go directly to the ER you should at the very least give your surgeon a call. I think it's difficult for a patient to determine how much they're actually bleeding. For one thing a lot of the blood will be swallowed so it's really hard to properly measure the amount of blood coming from the back of the throat. Any doctor will tell you that while 10ml of blood shouldn't cause any physiological stress it looks like a large amount of blood when you're wearing it on your shirt.