I have a 3 week old DS and have just started trying to express partly so my DH can feed him and partly as he clamps on my nipple and it has started hurting. When I express I try to do the opposite side after his feed but only ever seem to get 1oz when he feeds at least 3oz. How much is normal to get as I don't want to run out but it takes me 3 goes just to get 1 feeds worth?