Reflux?

My baby is 1 month old. 2ish weeks ago, we noticed her coughing after every feed like almost choking, and when we feed her it streams down the side of her mouth, she also wasn’t burping, and spitting up quite a bit. pediatrician recommended we go to a feeding specialist, and when we did, of course none of the things happening at home feeds happened during appt. I am pumping because she’s not getting a deep latch, so she’s still getting breast milk. She has only gained 8 ounces in 2 weeks and our pediatrician wasn’t super concerned but wanted us to try enfanil AR formula because he said my BM may be too watery? Is this common? I really don’t want to supplement, we started mixing the formula with my BM yesterday (after ped appt), and her stomach has been so upset. I feel like this can’t be the only option?