Have you tried laying a hot flannel over your breasts while you express? It helped me to get more colostrum out when I was expressing for Anna in hospital... I don't know if it would work for you

Worth a go?
Also, how long did you try expressing every 3-4 hours for? Because it will take some time for your body to recieve the message and increase it's production according to the demand... So I wouldn't give up on this one just yet if I were you.
I really hope this does work out for you two... I second what has been said about trying to put him to the breast again - his suckling really is gonna be your best bet for encouraging greater milk stores..... But if it doesn't work out it doesn't work out

- you'll know what's best for you.
Good luck, Jess.