I hve an ultrasound for nov 3 but im just rlly scared im not like small either i weigh 180
we first heard the heartbeat at close to 15 weeks, i think, but it was sooooooo very quiet, i could barely hear it, even when the midwife pointed it out to me. it also took her a looooong time to find it and she only found it after a second attempt. was much louder at 18 weeks. i would try not to worry, but if you like you could request an ultrasound. it also depends on the position of the placenta -- if it's in front it can muffle sounds and movement.