3 month old suddenly throwing up

My daughter was 3 months yesterday.  She has had problems since birth with vomiting (projectile at times and no not spitting up) she also has stopped breathing in the past and ended up in the hospital for two days.  They did a UGI with FT and diagnosed her with mild GER, placed her on Zantac and we continued to try different formulas.  The Zantac started to work after 3 weeks or else it was because we switched her to Similac Sensitive.  She was also started on 1/2 tsp 3 bottles a day of rice cereal.  She has been fine for about a month and all of a sudden started throwing up probably 1/2 of her bottles (the consistency is like oatmeal and a large amount).  She is at 50% with her weight and still still only takes about 3-4 oz of formula every 3- 4 hrs.   It is scary because she does this quietly and I found her today red and not breathing...I tipped her down and smacked her back...I was yelling to call 911 when she finally came around.  I will be calling her MD on Monday but it seems like she doesn't know what to do either.  Is there anyone who may have an idea of why she isnt tolerating her formula now so suddenly?

[peekawho]

I don't think I'd wait until Monday to call.   I would call right now.  

[kellym]

Did they check her for pyloric stenosis??

[natalie782]

When my son was a baby, he started to projectile vomit. I called the doctor and he told me that he just had a virus. i sat and fought with him and told him I thought my son had pyloric stenosis. my son did not vomit in the doctors office until after his examination. The doctor called the hospital and set up an ultra sound and found out that i did diagnosis him right. he had pyloric stenosis. tell your doctor you want an ultrasound done. I hope everything turns out ok for you.