need encouragement, negative pregnancy test

So my husband and I have been ttc for 4 months and I just knew this month was different I felt it in my heart! My period isn't due til Monday the 21st of August but I just took a digital first response and it says no. I'm so sad and I don't understand because my husband and I were busy all through and after my fertile window. There's no way the sperm and egg couldn't have met, so I guess I'm just wondering how come it's not working after so many tries. I use Opks and preseed. I'm just so sad right now, thanks in advance for your words of encouragement❤