Gas and bloating. Find out the problem.

I have been suffering from gas and bloated stomach for more than 2 yrs now..it started in 2015 and initially after consultation with doctor (endoscopy) suggested it might be a mild gastritis. I followed my diet closely and eating food in proper intervals it was almost under control. Again after some time it relapsed and still started troubling me. I will have continuous belching throughout the day and it will be severe after having food. I again consulted another doctor in 2016 who did colonoscopy, CT scan with contrast and biopsy (Small ulcer was found in terminal ilieum). Suggested ATK-4 tablet course for 6 months. Finished that at the beginning of 2017, but after that also i'm still having the same symptoms. Any suggestions on what test should i undergo to find out the problem.