Persistent symptoms after taking nitroimidazoles (like Metrogyl and tinidazole) often occur because these drugs only kill active parasites in tissues, not the cysts in your gut. To completely cure amebiasis, you likely need a 'luminal amebicide' such as Paromomycin or Diloxanide furoate to clear the remaining cysts. Additionally, your ongoing weakness might be due to post-infectious irritable bowel syndrome (IBS) or gut flora imbalance rather than an active infection. Please consult a gastroenterologist to repeat stool tests (ideally a PCR test) to confirm if the parasite is still present before starting any new treatment.