Hi @LuckyCat22 this sounds like hypoplasia which is what I have.
I wasn't able to produce enough milk with my first two babies but this was 15 and 11 years ago now and the support just wasn't available. I'm now 33 weeks pregnant and much better prepared.
I recommend finding a lactation consultant, you could start with La Leche League as they are brilliant in my experience. They can take a look and see if they think its hypoplasia.
Sadly, the breastfeeding world still doesn't recognise low supply and very often will ignore it rather than broach the possibility of it. If you can find a good LC who knows about true low supply then you're onto a winner. You may find you will never be able to BF exclusively but there are ways around it. You can buy or make a SNS system to work alongside BFing, and also pumping as much as possible too keep whatever flow you have going.
You can take domperidone which can help supply as well as many natural supplements (please research this as some can actually hinder supply depending on the cause of the low supply). You could start by taking Alfalfa capsules which you can take during pregnancy. Then from 36 weeks you could start taking Goats Rue (not before though). I've also heard good things about Black Seed oil. Avoid Fenugreek if you have any thyroid issues (it can dry your supply up if so)
I recommend a book called 'Making More Milk' by Lisa Marasco and Diana West, it is full of useful resources. Also, if you're on FB, there is a really useful group called IGT and Low Milk Supply Support Group. I've found it invaluable TBH.
You may find you don't have a problem. Even with hypoplasia, you could produce enough. It's mostly whether or not you have insufficient glandular tissue along with it, and you won't really know if you have a problem until baby is here, unless you've had problems BFing before.
Please let me know if you have any questions 