Help! Needing another perspective..

Has anyone ever had been pregnant but the tests keep showing negative? I had 3 healthy pregnancies and always found out I was pregnant right around 3-4 weeks. My bf and I are TTC and at this point, my period is 15 days days late, tests are showing negative as of 4 or 5 days ago when I last tested. I have not been under any more stress than usual, no significant life changes, diet or exercise. I'm going for bloodwork today but I'm wanting to know if this has happened to anyone else and they ended up being pregnant while I await my results which I won't have until next week.