What Causes High Fever With Black Soft Stools?

Hi my 2 yr old has had a fever for 2 days now. Last night I gave him a dose of motrin at 6 pm. At 9:30 pm his fever spiked to 104.2 and still was not time to give him another dose until 12am so I put him into the bathtub. I kept him in there for 30 minutes and it rose to 104.5, I called the doctor on call and he told me to go ahead and give him another dose of motrin but this time instead of the 1 tsp (cause hes 28lbs) to give him 1 and 1/4 tsp right away. In another half an hr it dropped to 103.8. All night it went up and down from 103 to 104 never going below 103. This morning at 7 was his next dose of tylenol ( I rotate between the 2) and his temp went down to 100.4 but now its on the rise again at 102.5 but now he just had a bowel movement of all black. No diahreah but it was very skinny and looked softer then it usually would. My question is is there anything that is going around right now that I should be worried about? Mind you he has had no other symptoms at all. Please help! My sons pedi is out of the country right now and on vacation and I dont really care for the doctor on call from previous reasons.