I'm 31 weeks my baby boy is the same as yours he will be super active for like 4 days straight and then very calm for like two days Specially when I am active. my doctor said it was normal babies develop their own patterns.
Go and be checked...
Don't count to 10 it's outdated advise as every baby moves differently and different amounts, it's important that you recognise your own babies individual pattern of movements and be seen if you are experiencing and reduction in movement.
Babies movements will change from kicks to more wiggles and squirms but the amount of movement should not change, and they will not stop moving due to running out of room.
My doc told me it was ok that it wasn't strong moving as long as he moved Atleast 10 times a hour!?so idk maybe you should count how much your baby is moving a hr!