2 Answers

If you are a relatively small person, your blood pressure is probably normal. However, low blood pressure and an increased heart rate can be a sign of dehydration, so my first question would be to ask whether you are drinking 8-10 large glasses of water daily.

To be diagnosed with tachycardia, or an abnormally high heart rate, you would probably have to be above 100 beats per minute - a little bit higher than what you have reported. But if you are a smoker, drink a lot of caffeine, or take any other stimulants, that will tend to increase your heart rate. In addition, if you are not exercising regularly (30+ minutes most days of the week), your heart rate will also usually be higher. Stress can also affect your heart rate.

If you are worried about your heart rate, you can try drinking more water, limiting your caffeine intake, practicing yoga or another form of relaxation, increasing your aerobic activity, and talking to your health care provider about your concerns. 

http://www.everydayhealth.com/forums/heart-health/topic/low-blood-pressure-and-high-pulse-rate

I hope you went to see your Doctor, and your ok now.