Still getting BFN.

Hello everyone, so I’m supposed to get AF in 4 days. My temps and dropping a good bit and noticed a change of .36 from this morning. My temp yesterday was 98.54 and today 98.18. So definitely a good bit of a drop. But, I’m STILL getting those BFN!! I’m using the Accumed cheapies from Amazon, and I heard they’re great for the price... So, I decided to give it a go. I’m supposed to start AF in 4 days. Do I still stand a chance? Thanks in advance.