21w2d.... Not feeling baby move.... Anybody else having this problem?

I am 21weeks and 2 days pregnant with my 3rd baby.... first 2 were girls and this is my first boy! By the time I was this far along with the others I could feel them ALL THE TIME.... I also see all kinds of posts where everybody says they're feeling baby move all the time.... I NEVER feel him moving... Not even when I lay flat on my back.... I'm really nervous something is wrong... Is anybody else this far along and not feeling baby move yet?