Hypertension and Rapid Heart Rate

Hello. I am a 26 year old female, healthy weight (5'5'' 122 lbs), but have recently been diagnosed with hypertension and tachycardia (rapid heart rate). Until recently, I always had low-normal blood pressure, but now it is ranging from 130/85-160/110. Also I constantly have a rapid heart rate while at rest, ranging from 110-160 beats per minute. I purchased a home heart and blood pressure monitor, most recent reading was 130/96 with a heart rate of 128 beats per minute. This machine, plus data from a Holter Heart Monitor did not indicate that my heart rhythm is irrregular (it's just rapid). My hands shake a lot. I do not engage in cardio exercise as much as I should, I think this would help with the blood pressure but my doctor said I am not allowed to do any exercise other than walking right now due to the rapid heart rate. I was given samples of beta-blockers (Bystolic 10 mg) to take 1 time per day; I have not started them yet- I'm hesitant to take them for some reason. Initial blood work and urine samples indicate my thyroid and kidneys/adrenal glands are functioning fine, so doctors are stumped as to why I am experiencing these symptoms. Any thoughts or recommendations? Thank you.

[R_WAGNER]

Additional Info: I do not smoke, and I rarely drink alcohol (especially since symptoms emerged). I used to drink 1-2 cups of coffee per day but eliminated all caffeine from my diet when these symptoms appeared.   My diet is very low in sugar. I wouldn't say my sodium intake is "high" especially compared to most Americans diets but this is one area that could be targeted and improved so I am working to decrease sodium in my diet. It is possible that stress could be a factor- I have a high stress job working with children with autism, and some personal family issues, but doctors continue to express that they do not believe stress alone could result in the intensity/frequency of these symptoms (especially because symptoms persist while I am completely calm/not feeling upset.)