My kids both have MFPI (multiple food protein intolerance) and these are some of the symptoms they had as infants:
– extreme gassiness and bloated bellies
– screaming/crying when passing gas
– mucus in the stool or vomiting mucus (now you could also see mucus like this when they have a cold, that’s different)
– overall irritability, “colicy” symptoms
– poor sleep because of discomfort
– reflux
– projectile vomiting
I didn’t ever see blood in the stool with my kids, but it could have been present without me knowing it (occult blood).
If this sounds at all like your little one, it certainly could be MSPI and in that case switching to a hypoallergenic formula (like Alimentum, Nutramigen, Pregestimil or even Neocate or Elecare) would be recommended.
Good luck!