I don't see anything particularly wrong with the resting rate, in terms of still having a healty sinoatrial rate (60-100). you'd have to look at EKG derivations to be able to certify any problem with the sinoatrial or atrioventricular nodes but I'm sure your doctor has looked at this already? now It's fairly improbable that caffeine would induce permanent damage to the NCX and cardiopulmonary nuclei in the medulla oblongae. Maybe (but it sounds fairly improbable) the caffeine hasn't completely been eliminated (how recent was this). maybe you've stopped excercising in fear of the condition? excercise keeps basal heart rates low. maybe you also take some average stimulants (like plain old sugar), and don't realise it. But seeing how self conscious you've become, you could just be inducing this mentally on yourself.
To potentially agree with coffee quaffer's possibility, it would be nice to know if you've had any other symptoms, like weight loss
, profuse sweating
, hyperactivity, etc. that could signal a primary hyperthyroidism
or something secondary to hipofisiary hyperfunction.