Help please! Advice needed

Hi everyone, im 13ish dpo today. Period due today i have an avg. 13 day luteal phase. Yesterday i got what seemed to be a BFP with FMU, very obvious full colour line. I was shocked so tested just 2hrs later and was negative (duh) i then tested 4hrs later and there was a good solid pink line again. This is all the same brand and same box tests btw cheapies. Then this morning i test with FMU and its stark white negative!! I am so confused. Of course i am going to test after a hold and get some frer but just looking for any similar stories and the outcomes? Im aware it could be chemical but ive never experienced one before so not sure how to determine that to be honest. Thanks in advance ladies, the pic is of the second positive test. I havent got pics of all in the time frames but now up to 6 tests 3 positive 3 negative haha