20 weeks and it feel like belly is going down...freaking out!

Hi I went to my anatomy scan last week and everything looked good and she was moving around.I do need to go back next week because they couldn’t get good pics of her heart but the heartbeat was 166 and strong so that made me feel better.

So why when I wake up my belly looks smaller? At night it seems a little bigger- is this normal?

Also I don’t feel her as much as I did last couple of weeks...

I hear stories about women losing babies at this stage and not knowing with no symptoms and it’s freaking me out.

Any advice?