Omeprazole for low weight baby - anyone else?

My baby is 9 weeks and currently in 2nd percentile, this a drop from 30th at birth.

Her last weigh in was on Monday, her dad took her to HV who have been zero help. She dropped to 9th at 6 weeks and they weren’t even going to weigh her again. On Monday they just shrugged and said “feed her more” my husband said she is EBF and they suggested giving her 40ml of pumped milk 3x daily on top of feeds. I called them to ask about getting her checked for a tongue tie and they said to go to one of the breastfeeding groups.

I went to one and the midwife or lactation consultant (not sure) watched me feed her and said everything looked fine with latch and swallowing and not like a tongue tie or any issues transferring milk, given I have pumped 120ML unlikely to be a supply issue. She said to try giving her the extra milk. I said I would but my baby has dropped almost 3 centiles since birth I don’t think an extra 120ml a day will cut it.

I saw the GP and told him she is very refluxy and spits up constantly after feeds and he said reflux or CMA sounds the most likely. She has been on omeprazole for two days now and I feel like maybe it is a little bit better? He told me to push the HV as they can’t refer me to infant feeding only HV can but the HV are acting like I’m being dramatic for being so concerned.

The whole thing has massively freaked me out, I’ve barely slept since that last weigh in. I really thought it was going to go up as besides the weight and reflux she seems fine. She has bad gas sometimes but she is alert, smiling all the time, lifting her head, has wet nappies and feeds at least 7/8x day. It’s made me feel like I can’t trust my instincts and am not a good judge of my child.

The plan is to go in next week to the GP and do a weigh in, if it hasn’t gone up they want me to cut dairy from my diet.

Has anyone else gone on omeprazole and seen weight improve?