Hello there,,,,well pretty sorry to hear about your case and to be honest i am hearing this for the first time that anybody is having gastric problems bcos of riding bike,,,,, but yes definately nothing can be ruled out... why dont you do just a simple remedy,,,,,stop riding your bike for a week and see if you have any change in your symptoms.if yes then dont ride the bike...and if your symptoms persist,,,then you definately need an appointment with a Gastroentrologist or an MD physician.
Next Steps
Please have a proper posture when you are working and also when you are riding the bike...lot of information is available on net for that.
Health Tips
Riding the bike may definately give you back problem.....but riding the bike and gastric problems are not that well documented in Literature.
Do resort back to me if you have any queries
Regards & take care.