Girls with home fetal doppler's..

Hey girls, I have a home fetal doppler that I have had sense I had my first child.. i loved that thing so much and used it twice every day till I could feel the baby kicking. I first got it when I was 9 weeks along and I could hear my baby instantly and easily! After my son was born I lent it out to my sis in law and now she has just sent is back sense I'm now pregnant with my second baby! I am only 7 weeks along right now so I figured it would be impossible to hear the heart yet, so I decided to try anyways but to not get freaked out if I couldn't hear anything. I think I may have heard the heart a couple times but only for a split moment, less than a second, then it was gone and I couldn't get it back. Maybe I was actually hearing something else and it wasn't ever the babies heart.. I'll be tryin again at 8 weeks. But I'm just kinda curious what your guys experiences have been with your doppler... what's the earliest you have ever heard your babies heart? Do you love your doppler or has it been something you regretted buying?