Have you considered temping? That could confirm that you are Oing. I wouldn't worry too much about how many days your cycles are since they are still pretty close in range. Mine range from 26-33 days. The positive opk is a good sign. Check out this website:
https://www.twoweekwait.com/articles/sperm-meets-egg-plan
The only thing I don't like about the SMEP plan is that it suggests doing opks once a day. Many people get a surge in the afternoon (around 2pm). Last month I got a negative opk at 4am, a negative opk at 6pm and then got a positive around 10pm. So, I would suggest doing opks at least twice a day.
Here's what I'm going to try (the first few are loosely based off the SMEP):
-Inseminate every other day starting CD 11, totaling 4 inseminations.
-Start opks on CD 10 and test 2/3 times everyday until temps confirm O.
-Continue rotating after insemination (10-20 minutes on each side).
-Take FertilAID and FertileCM.
-Get back to drinking a cup of green tea everyday.
-Drink lots of water.
-Quit drinking soda.
-Make healthy food choices (lots of fruits and veggies).