Hi there
You can't actually ovulate twice within one cycle (ie several days apart)...however, if you have 2 (or more) mature follies then they will release the eggs anytime within 24 hours of each other. I've had 2 eggs each cycle of Clomid so far & last month I released the first on night of cd14 & the second on cd15...so not exactly ovulating twice but releasing 2 within a day of each other. I released one from each ovary & could almost feel it happening & it must've been right that released first cos the pain stopped on that side afterwards.
As already mentioned, OPK's can be a bit misleading sometimes, especially if you have PCOS and/or are on Clomid and/or Metformin. OPK's detect the LH surge & you should usually ovulate 36 hours after this surge. Did you do the tests at different times of the day...they suggest you don't use them the 1st pee of the day (I only used them for a few months when we 1st started ttc)
Here's a link with info explaining why can't ovulate twice in one cycle but about releasing eggs within 24hrs...
http://www.ivillage.co.uk/pregnancyandbaby/fertility/contraception/qas/0,,3_160220,00.html
Also, a good indication that you're actually ovulating now is egg white cervical mucus (clear & stretchy) as well as a high, soft, open cervix.
Take care & good luck
Natasha