Plus size first time mom

I am 16 weeks and 5 days along, I had a doctors appointment at 15 weeks and 5 days but they had a hard time finding the heartbeat. There’s this little voice in my head saying “maybe it’s because you’re more plus sized the baby is ok”, but I can’t help but be a little worried they did an ultrasound and as soon as they started pressing into me to get a clear picture the baby was moving so they felt relieved but I still have this scene of worry. I just want to know if it’s because I’m bigger and that’s why they couldn’t find the heartbeat or if it’s because the baby is sitting in a position making it harder to hear.