Interested in starting bbt tracking!

I've been looking into it, and I already use several methods to track ovulation, but I'm considering starting BBT. I have a few questions that hopefully some of you seasoned professionals can answer! 😊

1. I hear it's the most reliable method of tracking, but I feel like there would be so much variation? Sometimes I sleep with little/no covers and the thermostat cranked to 72, and other nights my partner lowers it to 58 and I use a bunch of covers. Wouldn't that drastically change my bbt and give me inaccurate readings?

2. I've heard people mention a "dip." What is this, and when in relation to ovulation does it occur?

3. When your bbt spikes, is that before, during, or after ovulation? Is it the same as an OPK where it will predict ovulation the next day?

And for clarification, I'm using this to prevent pregnancy, and to learn/be more in tune with my body. So far we've been very careful, and I have regular periods so it's been easy tracking. I track CM and use OPK's, and I only recently learned about BBT, which I plan on adding to the regimen. We both know the best methods are abstinence and condoms obviously, but we both hate condoms and my partner has... software... issues... when we use them. So we're trying to be as safe as we can, while not using them. We have also discussed, and although we're trying to hold off on a little bundle of joy for now, we agreed if it happens sooner, we will be just fine. So hopefully no judgy comments...