Heartbeat

So I have been reading from other women that they can pick up a fetal heartbeat on their at-home doppler around the same time I am currently. I am 12 weeks today. I have not been very successful at finding the heartbeat, and my doctor said it was too early to check at my last appointment. I have not heard the heartbeat since my last ultrasound and anxiety is setting in :( My question is, is it more difficult to hear the heartbeat with a doppler when you have extra "padding" around your belly? I am normally around a size 16. Have any plus size ladies been able to find a heartbeat on their own around this time?