Oh... I would deft. do the hypoallergenic formula. How old your lo?
My son, now 14 mos. old could not tolerate anything but Nutramigen. It is very gross smelling and it took him a few times before he took it.
I sware we tried every single formula out there: Similiac (screamed and cried, gas) Enfamill (smae thing). Carnation Good Start (screamed even worse, so constipated and made his poop green), Soy (smae thing, bad bad gas). Gentlease (thought at first it was working, but no luck, back to screaming night and day), Lactose Free (no luck).
I would actually recommend Similiac Alimentum. It is just Similiacs version of the hypoallergenic formula and it does not smell nearly as bad.
The blood could have very easily from a tear, but if he is super fussy like that, try hypoallergenic. It is very very expensive, but I would call my doctors office all the time and ask for samples.
Good Luck, I have been there and still have problems with milk (or so we think), still trying to figure it out.
Wendy