Positive then negative 13DPO

Tested with FMU at 0945, got a faint line on a wondfo test. Dipped another wondfo test, another BUT lighter line. Soooo I ran to Walmart and got more test. Well a couple things held me up at the store 😡 I came home, dipped the FRER in the same FMU at 1130 and its negative. WTH 😭 !!HELP PLEASE!!