BBT chart questions for experts

I started bbt last month. I set my alarm for 5 AM every morning and take it save for a few exceptions. The one high temp last month right after my period was after a few drinks the night before to celebrate our anniversary, otherwise no alcohol.

My question is; I had a VERY clear drop the day AF arrived. I have been getting very hot at night and a little sweaty and my bbt has been steadily rising since that drop. Also AF has gotten very light; typically she lasts for 5-7 days and it is only day 4. Now, it hasn't gone above my cover line from last cycle, but does this mean I am getting a progesterone surge after AF? Could this be what occasionally causes my mid period flow lul and then picks up again after? Does it mean anything negative fertility-wise?

Thanks. From what I have read, my first chart is not "textbook" by is clearly biphasic. I am just trying to understand the intricacies of bbt.

Thanks!!!