Feeling baby move

I am 20 weeks and today I haven't really felt my baby moving as much as I have been. I can usually lay on my back or stomach and feel him/her moving around like crazy, and today it seems like little nudges here and there, nothing consistent like I'm used to. I've tried drinking water and ice cream to see if I can try to get him/her to move around but it doesn't seem to make much of a difference. I didn't do anything out of the ordinary or to strenuous yesterday to cause them to not be as active. Is this normal??