Quite terrified

I am quite scared from the stories that I read about going for the 12th week visit and discovering the baby had stopped growing, without them feeling anything!!! How is it possible not to feel anything? It literally terrifies me since I went for a check at 8 weeks (all was super fine) and my next one is at 11 weeks. How can I relax? How can I stay calm and feel ok? I am nauseous almost constantly and vomit sometimes, I'm exhausted and breast tenderness comes and goes. The symptoms don't keep me calm though...