Aimee, it's a great idea to keep a food diary (Good job, Sarah!
). Then take it to your doctor or a nutrition clinic and talk to them. It could possibly be chicken in combination with other things...or your current stomach ache with chicken could be a sign of a bigger problem--better to get it checked out and be sure.
The chicks gave you lots of great advice on protein. There's a lot out there!
Good luck, hon! This must be frustrating!