bloody stool once - milk allergy?

Pockety

Hi all.  I've never posted here before, but I'm hoping you ladies can help!

DS is 2 months old.  His poo is often green, but the doctor said that she's not worried about that at all.  Yesterday, once, he had a stool that definitely had a bit of bloody mucous in it.  Based on that, she told me to cut all dairy and soy until he's at least 9 months old, and then we'll see an allergist and go from there.  (The alternative being to use hypoallergenic formula, which I'd probably do - I travel a lot and avoiding restaurants/eating around all soy/butter/etc. doesn't seem feasible to me - tons of respect to those of you who do that.)  They'd also want to test his poo in a month to see if there's still traces of blood in it or not.

My question is, though -  do you think that this one instance is enough of a catalyst to make this drastic change?  Since I don't think I can actually do the diet, it'd mean switching from BF to formula, and that's obviously not reversible.  One instance just doesn't seem like enough of a reason - it hasn't been an ongoing problem or anything.  But then again, saying that makes me feel like a bad mom.  I obviously don't want DS to have GI bleeding!!!