A mistake most moms who have to pump make is believe the myth that because the amount you can pump has decreased, your milk supply has decreased. That is absolutely not true! But having said that, I understand how frustrating it is when what you can pump decreases. Reglan can help, so do talk to your doctor about that. But most importantly, make sure you are nursing the baby plenty when you are home with him. That is very important in keeping your milk supply good.
Try pumping while you are nursing him. This makes it so much easier to pump, as the milk is already there! I wouldn't suggest doing it every time you nurse, as that will just get annoying, but do it often, at least for awhile. You can also try switching pumps. Sometimes the pump that worked so well at first, doesn't work so well after a couple of months. It all depends on the pump you are using! Is it manual? You can get really good manual pumps! Medelas are the best, and they cost more, but are well worth it. If using electic, make sure it's a good electric, because a cheap electric pump is worse than a halfway decent manual pump!
You may need to pump a little more than usual if you are able. It's important to keep your breasts stimulated throughout the day. At least hand express milk when you are at work, but try to store what you express so you can use it later!
Please feel free to contact me personally. There are also other herbs you can try. I have a whole book about herbs and breastfeeding!
PS. As someone else mentioned, DON'T put cereal in the bottle. Not only is it a choking hazard, it's also a sure way to make that baby gain lots of weight that will just sit there, very umcomfortably. If your doctor suggested it (which now, every doctor suggests it for every baby,) ask him why exactly and for how long. Do what you feel you need to do, but if you continue, give as little as possible. That cereal isn't made for drinking. It's very thick and hard to swallow and digest