yah same EXACT thing happend to me...i was takin a shower thought...(i smoke in my bath room and blew it out the window and took a shower so i wouldnt smell) it was when i was a beginner too....fuckin freaked me the hell out....i couldnt sleep either cuz all i was focusing on was my heart beat haha....almost told my mom, but decided not too haha goooood thing!