Stomach Ache for more than 1 year.

Hi, I have been feeling pain for more than a year now on the left upper side of my stomach. And at the back of the same side. This pain doesn't let me sleep whole night and doesn't let me sit for hours. I got the Whole abdomen ultrasound done. It didn't show anything on this side. I had been diagnosed with Gastritis many times. And, I stopped taking any medications for it. As I was taking them for more than 7 years now. So I suspect if it could be a side effect out of it leaving infection into my stomach. I can't take meals properly. Stomach doesn't get clear usually. All the time I feel like my stomach is full and feels stressed all the time due to this. I have just consulted a doctor here, he suggested me the same medications that every doctor have been suggesting every time. But it never helps, the problem keeps worsening over time. However the the present doctor has suggested Upper GI Endoscopy but I am not sure if that's enough as more than a year ago I did that & it was clear.