Belly pain. How much time in this case.

Sir, Whenever I feel hot or I am in a hot place I feel ache in the left side of my belly.The same thing happens when I wear belt a bit tight.This ache starts from the lower left side of my belly then ihe ache spreads in the entire left side of my belly.In the time of ache I feel really weak.My whole body becomes weak.But after a certain time I have to poop.That poop is more liquified than normal.The symptoms I mention do not come all the times.In the normal condition I remain well.My stool remains normal.But only when there is a pressure on my belly or I am in a really hot weather for which my body has become hot only in those cases I feel the pain in the lower left portion of my belly.But then again if I come to a cool temperature then slowly my body gets normal. This problem is remaining for 6-7 months. Please tell me what kind of problem I am facing and what type of medicine I should take for how much time in this case .