Stomach pain- left side

hi, i am a 12 year old. i have been having severe/ or sometimes mild stomach pain in my left side, right below my ribcage, and have been getting it for over a year an a half. when the pain is severe, i get diareah. i am usually gassy, and it happens around when the stomach pain comes. i have been to the doctors, only to find that they couldnt get me answers. i went to the hospital afterwords, and had an x-ray and blood work done. the x-ray came back negative, which was a plus. i dont know about the blood work though. i am going to a gastronologist soon, but i need to have an idea about what is going on. i was told the doctors were leaning towards chrons diease, but they werent sure. please help, or just give me a general idea~ thank you