Pregnant?

So I got my iud out April 22nd, had just got off my period about 3 days prior starting the 15th if I remember correctly, we’ve been trying since took a test today it was negative according to <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">due date calculator</a> I could be testing too early, period is due about tomorrow , how long should I wait to test again ?