Faint BFP this morning, negative this afternoon

Carolyn
This morning I took a test with FMU, I am 10 days DPO and I got a faint positive, then I took another test this afternoon and it was negative. Is it possible the urine could have been diluted and that's why it didn't show up? AF isn't due till Monday. Advice please! Below is the faint line from this morning. Thanks!