OPK help!

According to Glow, my fertile window was supposed to start next week.  I am out of the country this week and took opk test strips with me to confirm my peak on the last day before I fly home.  On a whim, I took an opk test yesterday and got a positive!!  I took one today as well and it is definitely not at dark as the test from yesterday.  If I don't fly home until Friday, will I miss my fertile window this month??  Hubby is welcome to BDing ASAP when I get home but I'm worried that it will be too late.  Am I correct??