Thank you for the query.
Such symptoms can be caused due to diet causing bloating, diverticles or some other large intestine disease. It can be also caused by stress and can be not significant. However as in left abdominal area mostly large intestine is located it is advisable to have some diagnostics before diet change etc.
Before upper GI endoscopy
you should have abdominal ultrasound
and full blood work, liver tests, pancreas
test performed. After this tests, if no findings, colonoscopy
might be necessary especially if you also suffer from constipations, blood or mucus in stool.
Only after this tests you can explain your symptoms with bad diet. Beans, broccoli, cauliflower, cabbage, sprouts, onions and garlic can cause such feeling if large amount consumed. Physical activity always makes intestines to work property.
Hope this will help.