Visitinggreece i probab.got travellers diarrhoea. loose stools(1 day)abdominal pain,weakness,dizziness. tried nifuroksazyd.i feel weak.should i worry?

Yes: seek medical attention as you may be dehydrated or may have something else going on.

No would: Not worry as it is normal to feel tired after traveling especially weak after diarrhea. Rest and eat a bland diet and drink plenty if fluids. If not getting better seek care.

Stool cultures: I would have stool culture done to be sure it's not more than travelers diarrhea. an internal medicine/gastroenterologist would be able to help with that.