VFL 4 days in a row?

Hey, so I've tested a Vvfl on the 3rd, and have gotten a VFL on all of my tests ever since. I believe they are getting darker, but they are still not a BFP (some can't even see them). What's up with that? I'm buying a FR to try tomorrow morning, but in the meantime, anyone knows why the progression is so slow?

Here's all the tests, all pictures were taken within 5 minutes. The first tests had to be super modified to be seen and the last ones aren't modified (except for arrows). (Also, I am not 100% certain of ovulation date)

10 DPO:

11 DPO:

12 DPO:

13 DPO:

And I tried a different brand to compare (the top one was taken 3 hours prior to picture though)