Trouble hearing lung sounds

I don't feel like I've ever been able to hear lunch sounds while auscultating. I've used both a decent stethoscope I bought and the ones we were provided in class. I just hear the sound of my own breathing when in the back of moving ambulances- Ive checked different parts of the abdomen and back and just don't hear any meaningful difference when someone inhales in motion. What is going on? Ive been hesitant to start my ride time because of this. Not being able to hear it is new to me. I've been able to before when not moving.