My heart rate is between 96-108 while i am not resting. is that tacyhcardia. i weigh 270 and i am 18 years old?

Tachycardia: Tachycardia is a term for heart rate over 100 beats per minute, so yes, for part of your non-rest heartrate, it is a tachycardia. There are numerous causes for a tachycardia- some more worrisome than others. The most common is sinus tachycardia- that is, simply physical movement or mental stress increasing heart rate over 100 bpm.