Did your cold medicine include decongestants? Those can cause the palpitations and “racing heart” feeling you described. That’s why people with high blood pressure have to be careful to take only decongestant-free cold medicine like Coricidin. http://www.nhlbi.nih.gov/health/health-topics/topics/hpl/causes.html
When I was diagnosed and for the next 6 months or so, I was instructed not to do anything that would raise my heart rate – exercising (other than leisurely walks or gentle yoga), drinking coffee, taking decongestants or steroids, drinking alcohol, other grown-up things, etc. I was like, “Wait, what? Why can’t I take decongestants.” And then it was explained to me.
I would ask your endocrinologist which “triggers” you should avoid, if any.