Late period but false pregnancy tests?

[AlwaysPasta]

I've had PCOS since my early 20s (about 10 years ago). I have cysts and irregular periods but low/normal testosterone levels. For the last year, I have been without my Mirena coil and tracking my periods on an app. Last month, my husband and I have started to try and conceive. My normal cycle is around 37 days (+/- a couple of days) and I'm now at day 46 with no period. So, according to my average cycle length, I'm 10 days late. I had a tiny bit of brown spotting about 10 days after I was ovulating which I've read could be implantation bleeding? I've done a few pregnancy tests and they're negative, but I've never had such a long cycle before. Is it normal for false negative pregnancy tests? I'm feeling a bit confused and would love some help/advice! Are there any home-test urine pregnancy tests that are better for PCOS? I've read online that the 'early detection' tests can lead to false negatives in PCOS but I don't know how true that is