Pregnant?

My first day of my past period was November 13th. I was supposed to start on the 10th of this month and I’m now 4 days late. My Fiancé and I had unprotected sex on the 19th and 20th of November and they were 2 of my fertile days. One of those days I left my bottom propped up in a pillow. When should I take a test? What test is best?