Has this happened to anyone else?

So 4 days ago(1 day before expected period) I took a 3 pregnancy tests at 5 pm and they were all clearly positive. Now today(3 days late) I still haven’t gotten my period but every test is extremely faint to the point where I’m doubting if they are positive or not. This morning I took a Clear Blue Digital and it said “not pregnant”. The symptoms I’m having are lower back soreness, fatigue hard core, and my nipples are pretty dark and a little sore, I’m overly emotional about everything and I’m kinda nauseous in the morning but it goes away when I eat sometimes. I’ve been having heartburn and I never have heartburn so idk what that’s about. I have a gut feeling that I’m pregnant but the tests say otherwise. Any advise or stories would be great!