Hi there YummyMummy
Congrats on bf your lo either way

I really take my hat off to moms who express exclusively.
How often do you express and how much does your lo drink per day?
How much do you get out per session?
There are soooo many things to consider - stress, energy levels, getting enough sleep, staying hydrated etc.
The amount you express is definitely no indication of how much milk you have. Some women can express a lot & others don't get enough out with a pump or some will get more out by hand expressing than using a pump all together haha
What type of pump do you have? Have checked to make sure all the parts are still in working order and that there are no tears?
You can google power pumping and try that. See if it helps. What times do you express? It is always better to start off with your first pump early in the morning. Our supply is always a bit low in the afternoon.
Also paced bottle feeding is important to make sure baby doesn't overfeed with a bottle & causing you to not being able to keep up with milk. You can google paced bottle feeding.
Just try to stay well hydrated, oats is apparently very good for a mother's supply. There are 3 natural remedies you can try - Fenugreek tablets, brewers yeast tablets or Prolak. Both available at dischem.
I know a lot of people advice on Jungle Juice, BUT Jungle Juice does not contain any ingredients that has been proven to increase milk supply. But some mothers claim it works. Many mothers claim it doesn't. Other mothers develop THRUSH due to the high sugar content and some mothers start asking a few weeks later "how can I loose WEIGHT?" There probably is no harm in trying it. But do not drink it too often and too much.
Here are a few links to look at as well
kellymom.com/hot-topics/pumping_decrease/