If this is your first please try not to stress about not showing yet, I didn't show at all until 19 weeks with my first and I was fit and everything so it's not like she was hiding under fat or anything, it's just pretty normal not to show early with your first! If there's a midwifery centre nearby you might be able to ask them just to put the Doppler on for peace of mind, they won't charge you. Hope you get some peace if mind soon