I'm noticing that my heart rate sits between 85 to 105 when I'm just resting. I had an ECG done and my doctor mentioned I have sinus tachycardia, but thankfully no arrhythmia. I'm kind of worried, thoughdoes this mean I'm at risk for a heart attack or maybe a brain stroke? I'm only 19, so I'm not sure what to think.

In your case, since you are 19 years old and your ECG shows sinus tachycardia without arrhythmia, the chances of heart attack or stroke are very low at your age. To help manage your sinus tachycardia, you can try relaxation techniques, avoid stimulants like caffeine, and ensure you are well-hydrated. If your symptoms persist or worsen, you may consider beta-blocker medications like Metoprolol at a low dose under the guidance of a healthcare professional.