Dear friend, welcome and thanks for entrusting your query here at HCM!
I am Dr. Prasad Akole (Critical Care Expert- http://bit.ly/Dr-Prasad-Akole) and am glad to address to your query here.
Tylenol is not known to cause any heart rhythm disturbances.
Tamiflu could rarely cause heart
arrhythmia, but not so late. It is not a common side effect.
If you still have skipped beats and are an active flyer, it is better to seek
medical advice, get an EKG done (or a holter monitoring ) to look for any serious heart rhythm.
Your otherwise healthy lifestyle does not suggest any problem.
Rarely, viral
carditis (heart
muscle inflammation) can cause rhythm disturbances.
Do you get giddiness, sweating, breathlessness or any other symptom?
It is better to be evaluated by a physician.
I hope you are fully satisfied with the guidance I gave.
I would be glad to answer any further queries. Please ask for any clarifications before closing and rating this answer.
Thank you and Good luck!