second time moms and movement

Cassie
Update: everything is fine! I'm now 20 weeks and have started feeling regular movement. Had my anatomy scan a couple weeks ago found out we are having a little boy!! So excited and we can't wait. Thank you ladies for easing my mind. 
Any of you second time moms not felt movement yet? I'm 18 weeks 4 days and I haven't felt any movement. Is this normal? Should I be worried? I have my gender/anatomy scan on Wednesday and I'm afraid they are going to tell me something is wrong. Can anyone calm me down?