Not feeling baby move at 24 weeks

Im 24 weeks pregnant and going on three days that I haven't felt my little girl kicking or moving, she's normally very, very active and kicks me all the time. Three nights ago she was kicking like mad after not feeling her all day and the next day I felt her once and nothing today.

What I'm wondering is should I go to the ER? Or am I just worrying for no reason? My next doctors appointment is on Sept 15 but I don't know if I should wait that long, but I also don't want to go to the ER if it's not "ER Worthy"