Confused

Hi everyone, I did try posting in the tests group but didn't really get an answer...

I had what I think was a positive test (won't post pictures as I think it's against the rules?) yesterday morning on a 10miu test. Got excited all day, took a 20miu test this morning which was clearly negative. So I bought another 10miu and did it this afternoon- negative?! Anyone got any clue what's going on?!

I'm fairly sure yesterday's was positive not an evap line. However surely today's would also have been positive even though it was done in the afternoon, wouldn't the HCG levels have increased enough by now?!

I think I'm 12 dpo today (although the app is telling me I'm 10dpo). Starting to lose hope though after getting my hopes up yesterday!

Any help appreciated xxx