What Causes Frequent Vomiting After Feeding In An Infant?

Hi, I have a 7 month old child you had reflux as a 4 month old with the classic crycing, arching of the back and possiting small amounts of curdled milk almost instantly after feeding. This stopped around the 5.5 month mark Over the last 3 weeks she has been vomitting but it is distincitly different as in that it is 2.5/3hrs after a feed there is no warning and then she will vomit undigested milk or solids back up and then want her next feed - she currently feeds every 3hrs so its like she just holds in her to stomach vomits it up in time for the next feed Any ideas on what this could be?