My 1 month old coughed up blood,advice please?

My 1 month old son was diagnosed with bronchiolitis(sp?) on Saturday. Myself,and my 4 daughters kept passing around a cold that we just could not get rid of no matter what we did and unforunately my little man caught it. He has coughing fits and is congested. Well usually he never coughed up anything except for a little slobber but that was it.The cough hasn't made him throw up or anything and at the ER his blood cell count was good enough to not warrant a spinal tap being done on him. His regular pediatrician saw him on Monday and found that it was bronchiolitis as the hospital diagnosed,but said with colds like this it usually gets worse around the 4th and 5th day,and to watch out for wheezing and fever.If he has either of these symptoms he will have to be admitted to the hospital. He hasn't had a fever,or wheezing but this morning after I fed him he ended up having a coughing fit again and ended up spitting up some formula.After he spit up he still coughed a bit and ended up spitting up again only this time it was a light red color.It wasn't much maybe about a 1/4 of a teaspoon worth.My best guess is it was blood(maybe from an irritated stomach or sore/raw throat...but I still have an hr before his doctor is in the office so I'm looking for advice or suggestions on why he would spit up red/(possibly blood),and if I should wait for his regular doc to get in or take him to the ER. Mind you this...no fever,no vomiting or diarrhea,no wheezing,and only had the one coughing fit this morning.He hasn't coughed since this morning. Also just to be clear he only drinks formula so the red could not have come from something he had eaten or drank due to only drinking formula. Thanks for any advice or suggestions on what is going on or what it could possibly be.