New to ovulation testing- help?

Jessica • Edd 11/9 #3 after losing 6 mo old daughter last July & having a tubal reversal in September. Hoping for a rainbow baby!
Ok so I had 2 daughters previously then tied my tubes.  Unfortunately tragedy struck this year and we lost our 6 month old in an accident.  I had a tubal reversal 9/27 and TTC since! My first two pregnancies came easily within the first cycle.  This time, not so much.  I've been using the app tracking cycles and started using oviulation predictor tests.  So the app says I should ovulate tomorrow and been testing since Friday all negative.  I'm starting to worry does anyone have any insight? Should I not worry yet? Any trick to the timing of the tests?