aww hugs hun
you are doing an awesome job!!!
i too have walked in your shoes- i had twins at 30 weeks who had a 10% and 20% chance of survival

i found that my supply started to settle down at 4 weeks as well and had to work damn hard to keep it going.
but i did and i ended up expressing for 12 months!
blessed thistle tablets helped me so worth giving them a go- fenugreek did nothing for me
what also made a difference was my water intake and the time of day that i expressed. i always got more around in the AM hours than the PM hours so always tried to stock up and express 3 hourly overnight/morning and 4 hourly arvo. I also found that if i relaxed and read a book whilst i was expressing, then i would get more milk. also when you think you have got all the milk out, keep the machine on for a bit longer and see if you get another let down to happen!

also remember that your body is making enough milk for your bubbas needs now!! as she demands more your milk supply can go up as well. bubs are heaps better at getting milk out of boobies than machines!

The type of machine you use makes a big difference. For instance with a manual domestic machine I would get say 90mls but with a hospital grade machine i would get 120-150mls- so a big difference!!

this expressing is a hard gig but as you said, you at least feel like you are doing something to help!

if you want to chat at any time, please feel free to PM me!!
this is a tough gig that no one should have to go through- but we do and it does change you and shape you as a person. It certainly puts everything else into perspective. People that have healthy full term babies do not realise how lucky they are!!
hang in there hun and remember there are people here for you to support you!!!!
hugs