Late?

My period was supposed to come on the 19th. The day before which was the 18th I started feeling kinda sick and yucky which is normal for me the day before I get my period but then the next day came and I felt worse and never started and it's now the 21st and I still haven't started and I still feel icky and have a weird pressure almost cramp like thing happening in my uterus/ovaries/whatever. I haven't taken a test or anything yet just wanted to get some opinions. Should I wait a few more days to see if my period shows or go get a test?