Please help, first time tracking BBT

Kylee • Mon, Feb 01

Can something please help me understand bbt? I had a huge temperature decrease this morning. Does that mean I am about to ovulate? I know you can't confirm ovulation until your temp is higher for 3 days afterwards but should I BD tonight? I just took an opk test and it's still showing negative. I have never gotten a positive opk before so this is why I started tracking bbt.