Stressing about nothing ???

So this is my 5th baby. Was supposed to be 5th and 6th, but I lost one of the twins. However with my last 4 I had some serious like wake me up at night heartburn by now.. This time nothing. With all my babies I felt them move by now 17 weeks and 1 day. This time not really. My last appointment the nurse could not find babies heartbeat.. She tried forever. Finally found it, but said it was " surprisingly low in my pelvis still." She didn't seem concerned about it though, but said that's why I more than likely can't feel baby. I have had two scans where my surviving twin looks great.. I just still don't feel pregnant at all.. Like I honestly forget that I am sometimes.. I know every pregancy is different, but this is way different for me.. I just can't shake the feeling something is not right..