Slow weight gain, mucus in nappies

hello all

my three month old girl is EBF. She’s always had quite mucus filled nappies - my son did too and I’ve been told not to worry about it. She’s a happy little thing, hardly ever sick, very alert, and so drs are not fussed.

However, she’s slowly dropping off her growth curve and I’m starting to worry that she’s not getting what she needs from my milk. I don’t think the AMOUNT of milk is an issue, if her nappies are anything to go by, lots of wet and at least one poo per day, often up to 4. it’s not a dramatic drop, a few points every few weeks. but obviously I want to be proactive.

I guess my worry, with all the mucus and the weight loss, is…is it just going through her without her getting the nutrients she needs for growth? I don’t think she’s got an allergy because the poos are not generally explosive, she doesn’t seem in any pain beyond squirming for a fart sometimes, her skin is fine, etc etc. But my son was easily sleeping 8+ hours at this point and she’s managing about 3 which makes me wonder if she’s hugely hungry.

I saw the dr on Monday who said keep an eye. If she’s still dropping next Monday I’ll go back in but I guess I’m looking for some reassurance in the meantime. Has anyone else had this?