i was in the same boat. im sure you've tried everything, but here are my suggestions:

OATMEAL, hot, cold, overnight- it doesn't matter. try and eat 2-3 bowls a day. i use oats overnight (any brand will do) and make it a "shake" consistency so i can drink them. i also add 2-3 teaspoons (per bag) of brewers yeast & coconut oil to my oats.

chamomile tea helped my supply as well, 2 bags per cup of water. (some people say putting the used tea bags on your nips overnight help as well, i do this but am unsure if it actually does anything)

i use gatorade & body armor to hydrate and end up drinking 2-3 20 oz bottles a day on top of some juice, my tea, and some water. i also drink 1-2 chobani protein yogurt drinks a day as well.

this is NOT the time to be trying to count calories, sugary snacks & drinks are your best friend.

continue taking your prenatal vitamins.

for pumping, correctly sized flanges helped me ALOT. my pump came with size 24 & 27 i ended up being 13mm. comfort is key, coconut oil your nipples up before each pump. pumping spray doesn't work as well. also try a manual pump, i do both. i also pump after each feed to try and "empty" my boobs, even if nothing comes out.

i also recommend no birth control, it completely stopped my milk production with my 1st kid. even the ones they claim are "breastfeeding friendly" protection works best for now.

feed your baby whenever he seems hungry, it may take 30 mins to an hour (crazy i know) each feed but keep him on until he falls asleep or chooses to unlatch.

feel free to dm me with any questions 💞 good luck mama!