I'm so confused...

My period is 5 days late and I've been testing negatives! How long can it take to register on a test? We haven't been trying but we are not careful lol. With my son I found out I was pregnant 4 days before my period was due. It's never been this late in the past 4 years. I've been cramping for 2 weeks now and my boobs are a bit sore. Maybe I'm just over thinking and it's just going to be really late this month!