I Have Had A Rapid Heartbeat Over 120 Since Last

I have had a rapid heartbeat over 120 since last night before I went to bed. I went to work and got through my normal day but it continues and I have a slight chest pressure/pain. I just took my Prilosec before dinner for my heartburn/ GERD but it does not appear to have helped. I had problems with this n the past but never for several hours. I am a 62 year old female within 10 -15 pounds within my goal weight I am 5'3" and weigh @ 127. Please advise