BBT rises on period?

so the previous month I didnt understand bbt at all and my temps were super messed up cause i was doing it wrong, so i deleted and restarted with this cycle..

my bbt dropped 2 days after AF arrived and then dropped lower the 3rd day to like 97.7

but the 3rd day of my period turned into spotting and today i woke up (day 4) and im still barley spotting but my bbt jumped to 98.

(still learning all these temps and everything) but I usually have about a heavy 6-7 day period. not a slow lighter 3 day period and spotting.. and my temps seem off? lol im not sure why they dropped and jumped right back up today?

anyone wana humor me and give me some insight if they can?