Fluctuating BBT

Melissa • I`m 31 and a mommy to a handsome little boy.
This is my first month TTC. I've been charting my BBT all week, and it's really fluctuating a lot. Is that normal? I take my to temp as soon as my alarm goes off in the morning, and I've had anything from 96.8 - 97.5. I thought BBT was supposed to stay pretty constant, though? According to Glow and OPK I haven't ovulated during this time, so I'm not sure why there's such a range. Has anyone else also experienced this???