when u go on ur pubic bone leave it in one place for a bit then dont move doppler but point it in different directions around ur tum...u will deffo know the babies as it sounds like a train so a lot faster than ur own. if nothing then move it over a little bit as baby is soo small at 10/11wks that if u go too fast u could miss it. I always found if i got the whooshing..biut like a gail in ur tum then baby was never far.
Agree with Nemo - you 'll probably know it when you hear it - IS very like a train. If you go to www.mybump.co.uk ( sorry, too lazy to do a link!) then look under 'sounds' you can hear recordings of heart beats and that really helped me - at 10 weeks I found it but it wasn't easy and took ages the first few times.