If you've been feeling activity on a very regular basis and this is out of the ordinary, try drinking a little juice and laying down quietly to feel for movement. If another day passes and it's still not your norm, I'd give a call. While baby is still small, only you know what feels off.
I am 27 weeks and have this from time to time too- I’ve noticed his quieter days are often days where I’m more active and moving around a lot more which I think just makes him sleepier and less active. Obviously it’s worth talking with your doctor if you feel concerned at all but I think, just like out of the womb people, babies have different activity levels and alertness on different days too!
Re: 26 Weeks - Quiet days in womb