i have constant stomach pain and have to poo a lot?

[that_chinese_gurl]

well, i have been having constant stomach pain 4 like almost 2 weeks. i have been traveling 2 china and ukraine, europe. i had a few diahrea lappses in china and i felt stomach pain but i couldnt poo in europe. now, im back home in new york and i have a stomach ache every 1-2 hours and thats when i have to poo. it saps energy from me and i feel weak when i have 2 poo. is this normal and just how a stomach adjusts to a new countries food? none of my other family members that went with me experienced this as much as i have. and i dont think my 10 year old sister did at all. im 13 years old. whats wrong with me and how can i treat this?