Confused about lactose intolerance in 7 week old

[Sundayrain]

I posted the other day looking for advice on formula prep as my fully formula fed 7 week old has been prescribed lactose free formula. Following some of the replies I've been reading up and am now really confused. She was prescribed it by GP because of difficulty settling at night, crying episodes and infrequent and explosive runny poos...all of which I'm conscious could just be normal for her and don't necessarily need medicating. But since starting the lactose free formula her poos are suddenly more formed and more regular. So does that mean it's helping her?! I'm speaking to the GP again tomorrow as I don't really understand the plan, I know it's very rare to have primary lactose intolerance and she hasn't had a bug which could cause it. GP said sometimes they just have it and grow out of it by the time they're weaned? But that doesn't seem to reflect what I've read. I'm so confused!

What milk has she been prescribed?

It's Aptamil lactose free

How infrequent is infrequent? And how long/often are the crying episodes? I don't want to undermine medical advice and I'd follow their advice but you are right it is very rare for a tiny baby to be lactose intolerant. And many babies have crying episodes and explosive runny poos, that all sounds normal unless infrequent is less than once a week or the crying is practically all day everyday ?

@SecondhandTable infrequent poos are every 24-48 hours so still within the bounds of normal. They are very runny and explosive (soaking through clothes, then more on changing pad going up the wall etc!) and usually a bit of crying when she goes. Crying episodes are definitely not all day everyday, she is very unsettled when put down on her back but no obvious signs of reflux (4yo had it bad and it's nothing like that) so I'm thinking maybe that is just wanting to be held.

That all sounds really normal. Explosive poos and some crying are par for the course with newborns I'm afraid! I'm really surprised that a doctor would change a baby's milk based on what you've told me there, that all sounds like totally normal newborn behaviour. My eldest for example screamed most of every day and the GP didn't even consider trialling medical intervention until she was about 6 months old (and in the end none of it helped so it didn't seem a medical issue anyway). If I were you I would consider making an appt with a different GP because I really don't think it sounds like there's any indication for lactose free milk here.