I just don't feel pregnant anymore :(

Hi everyone I'm 16 weeks on Friday my bump has pretty much banished as well as all the symptoms surely I should be big by now?? I'm so worried somethings wrong maybe I'm just being paranoid is anyone else experiencing this?? I'm away on holiday and I just can't relax I had such a big bump at 13 weeks and it's literally gone there's nothing there except a very tiny one when I'm stood up this is my first by the way xx