stomach cramping in my 9 year old

My 9 yr old son has been complaining of "stomach cramping" and belching for the past 3 weeks.  He's had 2 viruses back to back (From what the doctor says) with fever/sore throat/cold.  He seems to now be over those symptoms but still complains of the "stomach cramping" and belching.  Could this be related to the motrin he has had during his sickness.?  I gave him motrin about every 6 to 8 hours. (the dosage for a 9 year old)  He was not eating much, so probably had it on an empty stomach. If the gastritis is related to the motrin? , how long does it last?  He hasn't taken motrin in 2 days and still complains of it. What can I do about it?  Should we go see a pedatric gastroenterologist? I would appreciate any help you can give me.