Is it normal to feel only what feels like movement from 1 baby? Can you even work out which baby you're feeling? 

I'm 19w, my last consultant appt was at 16 weeks. They didn't scan me, just checked the heartbeats which were both present. He said the babies were sat on opposite sides of my stomach (they're in 2 separate sacs). He said I would soon start feeling them. I am feeling the flutters daily, but only low down on one side. I feel nothing on the other side. would people think this Is normal? I'm due my 20w scan next week so not long to wait but am getting progressively concerned that I only feel on one side? Any advise is much appreciated!