Knew it was a bad idea to get one...

I am having such a hard time finding my babies heartbeat with my Doppler. I keep hearing a very loud kind of fast paced heartbeat but I think it's mine. I'll be 12 weeks tomorrow, so I thought maybe it'd be easier to find but I'm having no luck and I'm freaking myself out. At my ultrasound last week, the baby had a strong HB of 170 and he/she was twisting and dancing and now I'm worried again and idk what to do :(