Hey hun
i have the angelsound jumper and found babies heartbeat at 13 weeks, i didn't try before that. Even at 13 weeks baby was stupidly low down. I had to place doppler right above my pubic bone and kinda angel in downwards, if that makes sense?!
Also start at one side and work your way to the other using small circular movements, leave the doppler there a couple of mins then move on.
Also what lubricant are you using?? I used baby oil and found this works a treat, but some ladies recommend water! So you could give them both a go.
But as everyone has said, don't worry yourself, 10 weeks is still so very early and there is so much space in there. I'm 18 weeks now and find it really hard to find and keep heartbeat. So i've given up, i usually just plonker the monitor on and listen to him moving about instead!! Occasionally i'll hear his heartbeat as he moves past, but not for long!! Lol
x x x