As an STD assistant, I understand your concern about potential exposure risks. Sharing personal items like water bottles can potentially transmit certain infections through bodily fluids. However, the risk of contracting an STD specifically from sharing a water bottle is generally low. STDs are primarily transmitted through sexual contact or exposure to infected blood. To address your concern thoroughly, I would recommend consulting a healthcare professional who can provide personalized guidance based on your specific situation. My role is to offer general information while encouraging you to seek professional medical advice for any personal health matters.