Bottle feeding mamas

So quick question, I was breastfeeding and now I’m bottle feeding milk took 8 days to come and I have very low supply. I been bottle feeding every 2-4 hours. Ped. Recommended to do on demand since I am still giving her breast milk or what she can get out. So last couple of days she has been spitting out the milk. I’ll burp her and she burps and a little later she will seam like she is going to burn and ends out spitting up quite a bit for my liking. I called pediatrician and she said it was fine and normal. Wanted to ask on y’all’s opinion cause I feel like it’s a lot more than what she was spitting up before.