my last check up was at 15 weeks And everything was great BPM was 148 I have a check up tomorrow and…

my last check up was at 15 weeks And everything was great BPM was 148 I have a check up tomorrow and I am 18 weeks I am so nervous the doctor will not find a heart beat and something is wrong is it normal to worry and after 14 weeks should I have anything to worry about loosing the baby?