What’s the normal BBT of a 4-5 week pregnant lady？

Hello! What should the normal basal body temperature be when you’re about 4-5weeks pregnant? Is it cause for worry if it is slightly lower like 36.6 and going down to 36.4 the last two days? Does it signal low progesterone levels? I’m new mum and haven’t seen the gynecologist yet because I understand we only see them at 8weeks?