Welcome to HealthcareMagic forum.
Persistent loose and watery stool for 2 months is concerning. It is good to know that your stool sample is normal which rules out infective causes.
Oral hypoglycemic drugs such as metformin
are reported to cause loose stools in some people. I suggest you to discuss with your doctor and modify your oral hypoglycemic drug and see if your symptoms improve.
If symptoms persist even after the change of drugs you would need a colonoscopy
Hope this helps.