BFP then BFN

First let me say that I have infertility issues and endometriosis, so that makes me more confused. I just finished my last round of clomid in January, nothing happened. We weren’t even trying this month and I wasn’t even tracking.

Yesterday around 7pm, I went to target to buy a few things and decided to try and test just because. I’m used to the glaring BFN’s anyways, so why not? And per Glow, my period is due today. Much to my surprise, I got an immediate, semi strong but faint BFP. Not an evap, but an actual line with color. This was taken with middle of the day urine. Fast forward to this morning, I use the second test in the twin pack just to calm me down. And what do ya know, BFN! I have no idea why or what is happening. Any thoughts?