11-week-old baby drinking too little

Hi everyone. I have an 11-week-old daughter who recently started drinking very little from her bottle. She had breastfeeding for the first 6 weeks, but I stopped because I was getting overwhelmed. So we switched to bottle feeding. At first she had 90ml bottles, but we noticed she wanted more, so that went well. Then we started offering 120ml bottles which she drank easily. Everything was fine until 3 weeks ago, but since then she starts crying halfway through her bottle and pushes it out of her mouth. Because of this, she's been drinking too little since then, sometimes only 60-70ml. When we stop feeding, she sticks her tongue out, giving me the impression she's still hungry but doesn't want the bottle anymore. We've also tried distracting her when she starts crying, like turning on the vacuum cleaner, which helped sometimes but that's obviously not a solution... Usually it went well at night and she sometimes even drank a 150ml bottle. But that's not the case anymore recently... I'm worried because I'm afraid she won't get enough. She was born 3 weeks premature and already had a low birth weight, so she was on the lowest curve at the Child Health Centre. She still has wet diapers, but not as full as a few weeks ago... I was thinking maybe hidden reflux, but how do I recognize this? Any other moms with a similar story? Or tips? Greetings from a worried mom.