BBT in pregnancy

Hi, I have been TTC for over 3 years and when I saw the first positive test I was in heaven. Now I am 7w5d and every tiny change in my body is giving me anxiety and plenty of doubts. But to the point- I have been measuring my BBT for a very long time and I am kinda scared. All temperatures until 6w4d were around +0.4-0.6°C above the baseline, but suddenly from this day they are either on the baseline or -0.2°C below it. Should I be worried? Is it still worth to measure the temp at this point? I have no symptoms except sore breast and early ultrasound. I am freaking out that there is something wrong with my my beloved and long awaited baby.