I Have Been Having Heart Palpitations For A While But

I have been having heart palpitations for a while but all tests show nothing. Have just now had a be check of 91/61 pulse 91 feeling like I've run a mile but have just been walking round the house. After laying down 10mins later bp is now 97/67 pulse 64 . My blood pressure is usually under 100 so no worries there. It's the pulse I'm concerned about and feeling puffed. I am 73 years old dance 2or 3 times a week and weigh 53 kilos am 5foot 3 . In between times I feel fine. Except for sciatica problems caused from a bulging disc etc. thank you in advance for any comments. Trish email .