couldn't find baby's heartbeat.

Yesterday I went to my second prenatal appointment. I asked before going what would be done at this visit because my husband had to work, and I didn't want him to be sad he had to miss it. They said it's just a tribe test and bp test and they check the heartbeat. They don't do a sonogram unless there's a problem. So I'm laying there when the midwife comes back with the Doppler and tries all over my gbelly to find the heartbeat, but can't find anything. She says not to worry because sometimes that happens when the mom has extra fluff. But, I'm not that fluffy. I mean I have some, but it's not that low on me. She also said that at this time it's 50/50 that you should be able to hear it. I'm 13 weeks today, I thought it should be easy to find it at this point. She tells me that we're going to do a US, so I go to the other room where she tries for even longer to try to find the heartbeat. I can't look to see what's going on because that will tense up my muscles, which makes it harder to find. Now I'm starting to stress out thinking if I should have noticed any differences in my condition that could have been a sign something was wrong with my baby. On top of that, I'm there by myself. She finally says, "I can't find the heartbeat because your baby won't stop moving."  Thank goodness! What a relief! HR was 143, and everything is perfect. Also my placenta is in front, so that didn't help things either, and it will be a long time until I can feel the baby move. My husband is just sad that he missed it.