Need some advice!!

My 12 year old son had blood drawn a month ago and the results showed that he had a slight lower white blood cell count than normal (3800), and an above average count of liver enzymes. We waited a few more weeks and had him tested again only to get the same results. He has been referred to a Gastroentologist for more testing next week, but I sit here at work and wonder all day what is going on? Our family physician has not told us very much other than his levels are not alarming, but should be looked into. Is this the beginning of Leukemia or cancer? Should we be alarmed? He is above the 90th percentile in height and weight and is in excellent physical and mental shape. He is currently playing tackle football, which the doctor said is "OK". His mom and I are very worried and I am hoping I don't develop an ulcer. Does anyone out there have any words of encouragement or information for us. He has had an excellent health record over his entire life, but does develop canker sores in his mouth from time to time. If you have any information to share, I would love to hear it.