Dr. Hanif warmly Welcomes you! Thanks for consulting at my virtual clinic. I have carefully worked through your case, and I can realize your health worries. Being your physician, I assure you not to worry as I will take care all of your medical concerns.   Such stools are usually due to Intestinal bleeding. That is the reason of your dizziness amd weakness afterwards. Get your hemoglobin levels checked. Ask your physician for that and treatment. Reasons of intestinal bleed are a lot there. Yes one of them is something you ate that was contaminated and caused worm infestation (for example) and bleeding. Hope it helps. If you need further, detailed and quick assistance related to any health issues in future, feel free to ask me a question directly from my profile. Have a wonderful time ahead.   Best Regards! DR. MUHAMMAD M. HANIF USA