Intestinal cramps, blood in the stool and nausea all sound like worm-related symptoms to me...
Of course, it is certainly wise of you to doubt the seeds themselves, so perhaps as a first step you could purchase a second bag of seeds (a different brand or even from an alternate supplier) and soak them overnight prior to consumption. The soaking water may give some clue as to the state of the seeds themselves. (Floating seeds, disturbing aromas, etc.)
Oh, and I should state that I have eaten HUGE amounts of pumpkin seeds, and as a consequence have suffered intestinal cramps and nausea, but never blood in the stool. Blood in the stool caused by rancid/stale/mouldy nuts or seeds is not something I have heard of before; but I am always open to surprises...