Hello,
Thank you for your query at DoctorSpring.com
Greetings from Dr Satish
Gone through case history, I would suggest to do EKG if possible to do at the time when you fee the fluttering and in case it's not possible to do I would suggest to do Holter Monitoring which records 24 hrs EKG.
Check up your thyroid profile.
Sometimes even though pulse rate may be normal heart rate is high suggesting frequent ectopics or supravenrtricular tachycardia like Atrial Fibrillation .
Regards
Dr Satish