Huge Drop in BBT 13dpo

Sarah • MC Nov 2017; MC April 2018; MC Aug 2018🌈 Max Peter Phillips 26th June 2019🌈

Hi, had a huge drop in temperature this morning but cervix is high and feels very soft. AF due in 2 days give it take. Did a pregnancy test today and was negative. could the cold night last night have caused the drop? what should my cervix feel like so close to AF?