OK well he seems hydrated. that is a good sign. I would continue with the good start for now. the prosobee does not seem to agree with him.
keep an eye on the amount of spit up and the amount of wet diapers and stool frequency.
if he continues to spit up with the good start there are 2 possibilities and they are treated very differently
1. milk protein allergy - basically allergic to the protein that is in the regular milk. this is treated by changing the formula to a non milk based formula like nutramigen or alimentum. signs of a milk allergy are persistent vomiting, a rash or blood in stool. I think that you are ok on this front for now.
2. Reflux - all babies are born with some degree of reflux. Depending on the severity, determines what gets done about it. If babies are eating well and gaining weight appropriately then not much is done. Precautions to take at home include burping frequently after each ounce of formula, keeping him upright after a feed for 20-30 min and smaller frequent feeds. if this doesnt help, then starting a medication like zantac or prevacid is given as a last resort in a few weeks.
If the spitting up does not improve, he should be seen by the pediatrician on tuesday. If he starts to get worse before better, than you should consider the ER as a last resort but that is only is he is not keeping any feeds down and you think that he is dehydrated - sunken flat spot, no urine in 8 hours, very sleepy and lethargic.
I dont think that will happen but i am trying to outline all scenarios.
please reply with any further questions. Please take a moment to leave feedback if I have answered all of your questions.