Had v severe,brief diarrhoea 9 days ago.felt fine.stools now solid for 8 days but left with nausea,churning stomach,bad fatigue& malaise.not improving?

Many possibilities..: Most likely this was caused by a microbe; based on your symptoms it's likely a parasite such as Giardia or Blatocystis hominis but some bacteria can cause this too. You could see a Dr. for stool testing but the lab often may not find them even if there. Papaya seeds work as well or better than drugs for most parasite- chew 2 tbsp once every 3-7 days for 3 doses. If not better after that see a Dr.