I have high blood pressure?

I got my blood pressure randomly checked the other day. I'm 19,and was told it's supposed to be a small bit under 120/80, naturally, due to my age. but when he put the cuff on and it tightened it came off that it was 156/116 on check 1 and on check 2 it was 160/86!! I was shocked!! I have heart palpitations sometimes,but rarely and nothing major, lasts a few seconds, so i knew it was going to be either low or high; not normal anyway. But i really don't know why it's that high, that's really bad. I used to go to hospital a good bit due to illness and my pressure would always be low, as low as 90/50's or 60's at times. I don't understand how its so different now, my lifestyle hasn't changed much or anything, i am waiting on college exam results at the moment and am a bit anxious, but i really am baffled. Can anyone give me any explanation on why this may have changed so drastically in such a short amount of time??? since around december??