I had a difficult time hearing at first also. I went and checked everyones BP that would allow me, until finally it clicked. Now I can hear it all the time. I think the anxiety makes it very difficult when you are just learning. Practice as much as you can to gain confidence, and it will get easier. Also the double headed student stethescopes are really difficult to hear with.......is that what you are using in lab? relax.....it will get better!