Feeding stress

So I tried breastfeeding my daughter and lasted a few days (same as with my son). She had a tongue and lip tie snipped nearly 3 weeks ago. Oh my gosh, bottle feeding her has and continues to be a nightmare. I sit her up to feed and burp her every few onces. She is sooo gassy. She also obviously has a bit of reflux. The Dr gave us gaviscon to put in her bottles, but I feel like it made her even harder to burp. She takes forever to finish a bottle. During the night it takes up to 90 minutes, because she keeps falling asleep. We have tried changing her teats to faster and slower ones and we are using the best bottles on the market. She literally spends all day pulling her legs up. She only gets upset before she's burped or is going to throw up. I know newborns are often terrible at sleeping, so I often have her in a front pack. Anyone else got a super gassy baby? What are your best tricks please.