I took this FRER yesterday and it was obviously positive

So I took another one today and it was negative

(used pee I saved in a cup for when the test arrived)

This confused me so I took another one just now and it was positive again. I didn’t even hold my pee for longer than half an hour but the above pee was a 4 hour hold?

I don’t understand how that can happen unless I’m having a chemical? I’m about 10/11dpo...not entirely sure. Has this happened to anyone before and it turned out ok?