Movement

I know you are to start counting kicks or recognizing kicks at 28 weeks which I am right now. However, I wasn’t sure if it was different for multiples since you tend to feel them sooner. I have noticed reduced movement since yesterday but would this be because they are running out of space? I’m still relatively small and only gained 14 pounds at this time. About a week ago I felt them so much, moving and kicking each other and just go go go but this week it’s barely a small movement. When should I go in? When should I be worried? I know babies go through high movement and low movement and I remember having something similar with my singleton but I guess I worry differently with twins. Any help would be appreciated. I see my OB Monday but I guess I just want to understand others experience of movement throughout pregnancy.