Doctors stumped... Please, has this ever happened to your children?

[mature_enough]

The problem is with my exclusively breastfed son. I started seeing red in his urine or stool. At first I thought it could be the insert since I use cloth diapers and thought maybe there was a stain or my laundry bled together, until I noticed again on another insert which I made certain had absolutely no stains before stuffing his diaper. The next time I saw it I was worried someone may have pulled back on his foreskin as I had instructed my DH and my mom not to do as it could result in tearing the frenulum of my intact son, both of which said they never did.
I took my son to the children’s’ hospital since I couldn’t be certain it was not internal bleeding. I took a clipping of his diaper insert in hopes they could test the urine/stool sample instead of waiting for him to urinate or try inserting a catheter. The pediatrician on staff confirmed the red/pinkish coloring and took the sample to test. It did not have a trace of blood. The doctor was stumped. She then took another sample from a c-bag that was placed and again, it was clear of blood. She tested his stool and was again stumped when she found that there was not a trace of blood, so she sent samples to the lab… everything came back clear.
The red coloring still exists w/ my 7 week old son.
I have ruled out the possibility of an allergy since it is not blood, and I have ruled out the idea of something colored red since I have not had anything w/ dye/coloring and since my DD nurses tandem and does not have red/pink stools/urine.  
In addition, my son always makes a grunting noise, struggles to pass a stool, and seems oddly gassy compared to my 2 year old DD.

[margypops]

What are you eating , let us have a list of foods and drinks ..you eat/drink regularly if this is not blood, it is food coloring or similar and as you are breast feeding It has to be that..Many foods can color stool ,very often when babies have tummy pains its from mom drinking too much apple juice or similar..if your mom and DH look after him aswell is there anything they would give him ,how about 2 year old he would 'nt let baby suck on a red crayon or give him some of his own drink , ?