It's hard to say really. I've had implantation dips with my last two pregnancies.

I had a 36.7 temp at 8DPO then 3 day implantation dip at 36.4 on 9,10 & 11DPO then raised to 36.6 by 13DPO. +HPT at 13DPO but resulted in an early miscarriage.

I had a 36.6 temp at 5DPO then dropped for 2 days to 36.1 for 6&7DPO. It then raised to a high of 37.0 on 12DPO & I got a +HPT on that day. That pregnancy resulted in Brock.

I've also had a 3 day dip when I wasn't pregnant but it was not as pronounced as my implantation dips were.

I hope this info helps.