Breastfeeding - milk supply

I drink body armour which your allowed once a day or eat oatmeal cookies. It’s also important with hydration to be getting enough calories

As your supply is just being established, you’ll need to pump when your partner is giving a feed in order to keep your supply. So if your partner gives a bottle in the night, you’ll have to pump at the same time.
The only thing that scientifically supports supply is the removal of milk. Fuelling your body is important, but milk removal is the only thing that helps supply. Lucy Webber on Instagram is an amazing resource. Her book about breastfeeding and the fourth trimester is amazing, too x

That sounds like a dramatic drop, check your pump is assembled correctly, an air gap or misplaced flange could stop you getting any milk out - this happened to me a couple of times and it’s very frustrating!

Some pumps have parts that need to be replaced regularly so check that out

Keep latching baby and pump after feeding. It's supply and demand. The drop sounds like its been established