14 weeks pregnant and wondering!!!?

IM 14 weeks today! IM so happy, but IM also wondering about miscarriages I have heard that some people have them and don't even know it! I still have slight morning sickness, but it worries me still I go to my doctor once a month and hear it's heart beat to be sure but still! is there any thing I can do to know its OK?? IM just so worried! and I am also worried about the umbilical cord wrapping around its neck during delivery how is that prevented?? I know I sound nuts but the thought of losing my baby makes me worry! and I just need information thanks!