Dopplers...

This is stressing me out. One the 1st we heard the babies heart beat at the doctors on their Doppler. That day I tried finding at home with my Doppler an I couldn't find it. Almost 11w an still can't find it. My friend said she found her sons at 9weeks so why can't I find mine? Am I doing it wrong? I'm really starting to get nervous especially cause today was the first day I woke up with no morning sickness. :(