Some help advice wanted please 
I had my identical twin girls on the 4th Nov a little early at 34+3 weeks and had an emergency C section. I was kept in hospital and hand expressed colostrum. As babies were early they had not much sucking reflex so were being given premature baby formula top ups to encourage feeding, once my milk came in i was using the hospital pump and feeding expressed milk in bottles. Before giving the bottle the babies would do 5 mins on the breast to keep them used to it. They would suck for a few times and fall asleep (they have been asleep pretty much for the last 8 days!) they are getting much better at sucking and definitely latch on properly.
When I got home I didn't have a manual pump, I ordered one for next day delivery and it didn't come till yesterday, so I was expressing what I could by hand (10/20ml) and topping up with formula but my breasts were engorged. When pump arrived yesterday afternoon I pumped and got 160ml! but since then whenever I've pumped I can only get 20ml, I can feel and see that my boobs have gone down 
I really want to breast feed!!!!
How can I increase my milk supply?
I am pumping anyway and still putting babies at the breast before their feeds to try and stimulate the flow, and alternating give the 20ml I can get out to each twin, every other feed.
Please let me know if there is anything else I can do, eat, drink or take to encourage this. My girls are getting stronger every day, more alert and sucking for longer and I feel confident to breast feed but feel like my body is letting me down.
Please help 