18 weeks and not feeling any movement..

Em

I'm 18 weeks along today and feeing no movement. I mean none at all. This is my second and I felt my first move at 15 weeks and felt tons of movement every day by 18 weeks. I felt this baby move around 14 weeks and a little at 15 but it's stopped since. Should I be concerned?? I'm starting to get very worried. Next ultrasound/appointment isn't for 2 1/2 weeks...