Do you all buy the baby fetal Doppler? I on my week 15 but I unable to hear my own baby heart beat

I baught it at 1st trimester. It helps me a lot throughout my pregnancy. Now I’m GA 35+ wk, still need to check my baby’s heart sound anytime I feel less movement and anxious. Before 24 wks, you must find it very low near your groin. If you cannot find it, wait a while then do it later or use more ultrasound gel. It’s not that easy when the baby is very small.