No period but not pregnant??

So I’m a week late on my period but I’ve taken 6 (SIX) pregnancy tests over the course of the last 3 days and they are all a resounding negative but I have no idea why I would be getting negatives if I have no period. I’m not trying to get pregnant but I did get my implant taken out about 6 months ago to give my body a rest after 6 continuous years of birth control. While I had the implant I was having 2 periods a month, but after I got it out I had a very regular period and this is the first irregularity I’ve had. I plan on calling my OB on Monday if i still haven’t gotten it but is there any reason I wouldn’t be getting my period while also pulling negatives on tests?? Thanks. 💕💕