How is her weight gain? That is the best indicator of how she is eating. I think most pediatricians let you just come in any time to do a weight check. Mine said if I ever felt like he wasn't getting enough food to just walk in. You could do that once a week between appointments just to track it. But if there was something wrong with her weight the docs would be all over it at this point I think.
My sister's son spit up constantly. Like more than you would think possible. During and after every single feeding, and even after a while when you would think he wouldn't have anything left to spit up. They checked him for reflux and he didn't have it. The doctor told her that some babies don't have a completely closed valve between their stomachs and their esophagus. It's pretty common, and it can take up to a year to finish completely forming. It isn't anything to worry about as long as they dont show signs of dehydration and are gaining weight appropriately. It is just a big inconvenience because you are changing clothes all the time. My sister never left the house without at least 5 bibs. It freaked me out at first, but he was always fine. He wasn't even bothered by it like babies are that have reflux. It was almost like the food just fell out of his belly, not like vomiting at all. By the time he was 6 mos it was much better, almost gone by 9 and completely gone shortly after his first birthday.
If her weight and hydration are good, it is most likely this. Ask your doctor to give you information about what it could be at her next appointment instead of just saying "it's fine and normal". It probably is fine, but sometimes they forget we don't know everything that they do about how babies' bodies work. And don't hesistate to get a second opinion if your doctor is not able to address your concerns in a way that makes you feel better. Keep her upright after every feeding to give it a chance to settle. Try not to jostle her too much. And just take every feeding nice and slow, with lots of burping like you are doing. My sis was never able to switch to a fast flow nipple when he got older because that would do it, and she had to try a couple different bottles to find one that gave him the least air in the formula. Hope that helps, good luck.