Over the last few days I have been having a strange sensation in my chest. It feels like my heart is slamming against my ribcage. It's uncomfortable but only lasts for 1 beat and occurs 12-15 times every hour. I am 36 with no cardiac history, I exercise frequently but still have a BMI of 31. I also have been on cefuroxime for a week due to a second sinus infection/bronchitis in the last month. Is this normal? Is that what palpitations feel like?