Help!! Am I pregnant or not???

So today will make 18 dpo and I haven't started my period yet. I was supposed to start on the 12th. Me and my boyfriend started trying on April 1. I haven't taken a test yet but I haven't been cramping at all like I'm about to start or anything. Should I take a test now or wait a little longer? I haven't been able to eat much because when I do afterwards I started feeling sick with just about everything. Help!! I don't know what to do and not sure if I'm  pregnant or not!!!