Momkate, I'd follow up with a GI person. Spending a bit more money is a small price to pay to try to get some answers. And if it puts your mind at ease, it's worth it.
CBC is not the only blood work that should have been done. If that's all your doc did, then I'd certainly check with another doc.
My 16 month daughter had a liver scan this week that showed a slightly enlarged liver which was suspected and we have just been left also with no explanation of why or what futher tests will be done.
I followed up with my GI doctor for my son and she said it may have been a virus. However, they are now testing for food allergies which can sometimes cause this to happen too.