I know doctors say babies have a turn-off mechanism when it comes to feeding, but in all my years of watching children, I've yet to meet a fussy baby who wouldn't take a bottle just to be soothed, hungry or not.
My personal thought is that premies haven't fully developed that turn-off switch. I say that because I babysit a little boy who was born full-term and a little girl who was a premie (by 3 weeks). They're almost the same age, but the little girl is slightly older. The little boy eats 4 ounces every 3 hours like clockwork. He's the perfect size/proportion (to me).
Per the parent's instructions, the little girl takes 8 ounces every 3 1/2 to 4 hours - and would take more if offered, usually spiting up at least 2 ounces, and is very, very chubby (nearly twice the size of the boy). She can barely move, but the little boy is already capable of sitting well in the Johnny Jump Up and is learning how to use it! I don't know if this has anything to do with her being premature, and as I understand it, her doctors are not concerned about her feedings or weight at this point.
I've never heard a doctor say that there's a problem like that with premies, but I have observed it in a couple of babies now. It may be that your little one just needs to eat a smaller amount more frequently.
On the food front, I have known parents to introduce a small serving (1-2 ounces) of rice cereal in a feeder (since they don't get what the spoon is for yet) before bedtime if the baby wasn't sleeping at night. My nephew, was the exception - he took several ounces of cereal at each feeding at the tender age of 4 weeks because you just couldn't feed the child enough!
Our pediatricians, however, were adamant that no foods or juices be introduced until the 6th month due to food allergies, tolerances, etc. (Turns out, that was a good thing - my daughter is sensitive to wheat products.)
Nevertheless, I would call the pediatrician and see what they suggest since they know the trend in his growth an development. Good luck!