Not sure when to test...HELP Please

My fiancé and I have TTC for 5 months  now with no happy lines yet. AF was due around the 15/16 so I'm 3/4 days late. I really want to take a test but afraid of being let down. I have a pretty normal 28 day cycle and consistent periods. Since last Wed I've been nauseous on & off also the past 2 days my sense of smell is heightened. Please give me some input