Constant Fear

Hello everyone, I'm currently 17wks 5days and I'm living under constant paranoia. I'm scared that when I go to the doctors office today for my checkup that the heartbeat won't be there. I was like that for my 14 week check up and then my first US at 8 weeks. I guess I've been like that since my first us that there wasn't a fetal pole yet but they said I should be 8 weeks and I was only measuring at five weeks. I'm still getting sick every once and a while and I'm just terrified that there won't be a heartbeat. 
Anyone else ever have this fear?