Weight loss/weight Gain/feeding

[BRSMum]

3 week old baby still not back at birth Weight so still under midwife care but what is confusing us is at week 2 he gained 125g over one weekend to get him 55g below BW, then -(because of jaundace) he got weighed 3 days later at H and was only 40g from birth weight so out on 15g but then at the midwifes the next day he lost 45g again. What is going on.. His feeds have been regular as clockwork, we are combi feeding due to weight loss. Midwife told us to see a GP, had an app Friday and they didn't seem to worried but will see him this week anyway! Should we be worried?

Is he still jaundiced? Because our DD was slightly yellow for a long time and this had to do with tongue tie. She couldn't drink properly, didn't take enough of the fatty hind milk and therefore stayed jaundiced.

She also clicked with her tongue while eating. Bottle was also an issue for a while.

It would be a good idea to weigh him around the same time on the same scales. They should be calibrated but still. Might be part of the explation in weight difference.

I would also get a lactation consultant, not just anyone but an IBCLC, to check for tongue tie, lip band tie and breastfeeding latch.