My daughter threw up regularly, daily, (sometimes more) until she was about 3.5 years old. I know the helpless feeling of having to carry around barf bags, gloves, towels, and clean clothes everywhere we went. Her car seat cover shredded in the washing machine because it was washed so much.
She was VERY picky, gagged on certain textures, and constantly had hiccups. From the age of 14 months to 3 years, she did not gain one single pound, she actually lost a few. The pediatrician she saw at the time was not concerned. I finally changed pediatricians, to see the one I saw as a child. The new pediatrician ordered an upper G.I. and a swallow study (that was NOT fun). He diagnosed her with reflux and delayed gastric emptying and put her on medications. The medications helped, but did not stop the vomiting. He was concerned about her lack of weight gain, so he had us give her 3 bottles of pediasure a day since getting her to eat was a battle. Sometimes she kept it down, sometimes not.
We went to a speech pathologist, but my daughter would NOT cooperate under any circumstances. She still vomits occasionally, and it isn't like a normal kid, it is projectile, like a baby. Its usually when she is sick, carsick, or upset. She has gradually put on weight, and at almost 5, she weighs 36lbs. Getting her to eat is still a battle sometimes, but there are foods I can count on her eating. So, even though they tell you not to be, I am a short-order cook for her.
It was a very hard time for me as a mom. I felt so helpless. My advice to you is to persist, get a new pediatrician if your current one won't listen. You know something is wrong, don't rest until you get help for your daughter. Someone will listen to you eventually. It is hard enough to see your child sick, and it hurts even more when you feel like you can't do anything to help them. Your daughter needs to have tests run (such as an upper G.I.), she needs to be checked for food allergies (they can cause reflux), and she needs to be evaluated for a possible swallowing disorder (like dysphagia). Good luck to you!
I hope you find the help your daughter needs. (((Hugs!)))