Babies heart beat at 35 weeks??

I just went for my appointment at 35w4d and the doctor had a hard time finding the babies heartbeat it sounded like he was facing my back and we couldnt hear it good. And it was only 130. It's been 145-150 at every other appointment. And I'm a little worried about him. I don't want anything to be wrong! She didn't seen concerned but she did spend extra time trying to hear it clearer which made me think she was worried but didn't say anything. Idk. I go back in a week but I'm just curious is anyone elses LOs heartbeat slowed down that much at this stage?? I really need some reassurance..