Ditto to what Gigi said. I think you should do a HPT. My doctor also explained to me that the OPK tests can detect LH or HCG. So you might be pregnant. I don't think (other than that) that there is any reason for having a + OPK test that late in the month! Good luck! :)
Have you taken a pregnancy test? OPKs mistake hCG for LH and will go positive if they are picking up the pregnancy hormone. I would give it a check. I got a +hpt at 11 dpo, so maybe your OPK is picking up hcg. How come you are doing OPKs on cd26? If O was confirmed by the rise in temperature, you dont need to worry about it anymore.
I am 13 wks pg and i just tried out an opk to see what it would do, and it went positive.
Best of luck to you!
I have never continued to take opk's after confirming ovulation, so not sure if it is normal to get a second one. I have heard that it is rare but possible to ovulate twice in a cycle. I would BD just in case! Have your temps stayed up since the rise after the first + opk?