Almost positive OPK 2 days after AF was due

Today I am on CD 43 and AF is 4 days (day 5 today) late according to my period tracking app. The past 3 cycles have been exactly 38 days long so this throwing me off. I've got no AF nor preg symptoms thus far, at least that I've noticed.

On 8/21, the day before AF was due, I decided to use an opk out of curiosity because I hadn't had any cramps or other indicators that she was on her way. I also had a hunch/feeling that I might be pregnant. Firstly, a line popped up which hasn't happened outside of a fertile window for me before. I've used an opk ever day since then and they've progressively gotten darker, the darkest being on 8/24 but not quite positive. I've got 2 BFNs so far on FRER and FR digi(which I hate) two days apart, last test on 8/24. OPKs have lightened up the past 2 days so I'm very confused.

From what I've heard it's possible for some women to get an LH surge before AF but I've never seen it in any of my other cycles. I've also heard women have gotten BFPs with positive and almost positive OPKs.

Has anyone had either of these experiences and if so, what did your OPKs look like and how long after did you get BFP or AF?

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