Hi, i'm an 18 year old girl and lately i've been getting really shaky and my whole body feel tense. my heart feels likes it's beating really fast?

Panic disordor: It is very possible that you are suffering an anxiety/panic disorder, especially if someone in your family has similar symptoms/diagnosis as well. It is not common to have heart disease at 18. Asthma can make you short of breath but often not shaky or feeling tense except during an asthma attack. This seems to bother you and so i would recommend consulting your doc for eval/treatment. Good luck.

Physical exam : First get a physical exam to rule out medical causes. Tell your md about where and when it happens. Then consider anxiety related causes and seek counseling if appropriate.