I had sex saturday october 27th. unprotected. then i received a yes on my opk on saturday november 3rd. how likely is it that i could be pregnant and?

Possible: Repeat the test. Most are accurate 7-20 days after conception.

Unlikely: If the ovulation predictor was positive on november 3 then ovulation wouldn't occur until 24 to 36 hours later. Intercourse occurred approximately 8 days before, the likelihood of conceiving from that episode of sperm exposure is highly unlikely.

Possibly: You always have to rule out pregnancy. Get a home pregnancy test. They should turn positive about the time you're a week late. If it's negative, repeat it and call your doctor.