My ecg said sinus tachycardia with non specific st changes. should i be worried.?

Not necessarily, but: Sinus tachycardia, or a fast, but normal heart beat, is not in itself a problem, but may be a sign of an underlying problem. If your echo (ultrasound of your heart) is normal, it is likely due to adrenaline surges. I think you asked about palpitations earlier, same answer. Limit simple carbs, exercise regularly and eat small meals frequently. Insulin resistance leads to coronary artery disease.

First question: The first question is always to figure out whether that's a determination by the ECG machine or by a capable md. The computer is almost universally wrong :) nonspecific changes are just that - they mean little unless there's a broader context of your health and heart to put it in. Most of the time we treat it as a benign finding. I'd have to see your specific ECG to reach that conclusion.