A temperature drop in the basal body temperature BBT chart about a week or so after ovulation could well mean that there was implantation and pregnancy has occured.

Implantation is supposed to happen about a week after ovulation so your timing yesterday was perfect for implantation, the attachement of the fertilized egg into the uterus. There are some who believe that the basal body temperature could dip on implantation, so what you saw yesterday could have been the so called "implantation dip".

If you are pregnant then a blood pregnancy test is usually positive 3-4 days after implantation, and the urine test is usually positive 2-3 days later, about a week after implantation.