Loose stool. I think what should i do!

I have loose stool for 2years in the morning if I change my bowel habit it is normal but everyday in the morning I have loose stool i went to gastroenterologist he advised ultrasound the report was normal and gave some medicine just for satisfaction he told it's lifestyle related after taking medicine for 3days nothing happened but from fourth day my stool in morning was normal for about 15 days it was normal but from a week now it's loose just like before I don't understand why can it be medicine killed bacteria but medicine was for 5days only so after the effect of medicine went I had loose stool the medicine he gave was metronidazole ip400 mg and rifaximin ip200mg twice and thrice a day how come after taking antibiotics my stool was normal as I have this problem for years but right now it's back to same no improvement I think I am losing weight because I can't absorb nutrition from food my muscles are also not developing malnutrition I think what should I do