20 weeks 3rd pregnancy cant feel baby move very well!!!!

Hi just wondered if anyone is experiencing the same thing as i am. i am 20 weeks +3 days pregnant with my 3rd child and although i can feel her when i really concentrate occasionally im not feeling very much. I have been feeling the same movement flutters since i was 14 weeks pregnant but she doesn't seem to be getting any stronger should i be worried???? My 20 week scan is tomorrow morning xx