BBT Charting Help

So I ovulated around the 15th of Sept. AF was due on the 1st of Oct. my norm bbt was around 97.2-97 I was sick for about a week which caused my temp to rise to about 98 for 3-4 days. Now it hasn't dropped down to my norm 97-97.2 it's stayed slightly higher. I've tested with opk on I wanna say the 7th or 8th and it can back postive, the next two days came back negative with the opk. Then took a hpt on the 10th with another negative result. I know on the 15th of Sept. I was ovulating I had all the normal signs including a pos opk. What gives??