Have you tried switching phalanges? I had the wrong size and got more milk after switching it. But I still don't get "a lot" of milk. I'm supplementing too but only because I'm super busy and don't have a lot of time to pump usually. A pump never gets what you actually have. Feeding the baby often creates more milk over time. You'll produce more milk usually in the early morning or late at night. My boobs don't get engorged either and I can go all day without feeding on one or the other.
My baby is 7 1/2 months and only weighs 16 lbs. it's normal for some to be petite. As long as they are getting enough wet diaper as day that's good. Are you on any medication? Some will slow down your production. I believe benedryl is one of them.

@jgarciamua they've told me the same thing my doctor tells me and I tell them it's not working. And as far as they know now she's strictly on formula so that I can get my daughter enough food in the month because if they know if I'm still breastfeeding they'll take it away and that's her main food source

@moonslugg my baby girl has been on formula since the hospital. She's gained plenty of weight because of it. Been supplementing whatever milk I pump. No more than 4oz a day, and that's if I drink my mother's milk tea

@roxxipup249, have you tried
Talking to a lactation consultant? If you have wic you can see one for free

@lauramichelegord @jgarciamua after pumping I've tried hand expressing and I only get a few drops out after 20 minutes on each side. I've been drinking mothers milk tea twice a day and I get a total of 4oz pumped a day. I had problems with DD gaining weight the first week because I wasn't producing anything. I can't get her to latch on correctly. She has a shallow latch that pinches off the supply. Causes more pain to have latched on than it does to pump

If you have to formula feed don't ever feel guilty. A feed baby is a happy baby. My baby basically grew up on formula, she's a happy chubby and healthy baby :)

I did, no matter what I did I would only produce maybe 1-2 ml per day. It was so hard. I literally tried everything, I worked with lactation consultants, my doctors and I just couldn't produce anything. I finally stopped pumping/ trying everything I could do around 4 months.

The more you latch the baby the more you produce. Whatever you pump does not indicate how much milk you produce. And yes stay hydrated

^^^ Also make sure you're drinking plenty of water and eating/snacking throughout the day. It can have an effect on your supply too.

Are you exclusively pumping? Some women do not respond well to a pump. They could be producing plenty, but the pump doesn't show it. Try hand expressing. It takes much longer, but you'll probably have better luck. You could also try heat compressors before doing so to help with the flow.