DARK OPK at 5/6 DPO?

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Hey, all! I have been BBT-ing every morning to confirm ovulation - sorry for my sporadic chart, as I missed a few days after my period. Also wondering if the very low temp 2 days ago was due to sleeping with my mouth open? Anyhoo - my chart thinks I ovulated 5/6 days ago - yet today, I had a very large temperature dip I got BLAZING dark OPK. Took another one to confirm as well - anyone experience something similar? Any insight is greatly appreciated :) This TTC (trying to conceive) thing is new to me - we are on month 3 and there's so much to learn!