How do you take your bbt

Orally? Vaginally? Anal?? I know to get the most accurate that we have to take it from the same place that cycle. I do it vaginally. This time I wanted to see if my temps came out differently. So I first test vaginally and came out 98.1(close to my coverline.) Then I tested from my backside and it was 98.6 (I cleaned my thermometer with my alcohol wipes before I did that) have any of you girls done. Once tested viginally and switched it up a different cycle?