BBT question (pls help)

Danielle

This is the 1st month that I am tracking my BBT for baby #3 for me and #2 for my hubby. My BBT has been up and down for the past few days. What does that mean?

97 up to 98 down to 97 and today back up to 98.

Ps we had a MC 6 months ago and are TTC for 2 months now. We got pregnant the last time out really trying.