Ovulation after D&C question

I had a D&C on July 14 and AF didn't show until September 17. My levels are finally down to zero (at least I think zero since a pregnancy test came back negative). I wanted to see how regular my cycle would return so I started using OPKs on Sunday and had a faint line. Yesterday it was much darker and seemed positive. Today the line is almost gone. Anyone with experience know if this is typical level shifting after a miscarriage or might I have ovulated in the last 24 hours? Any insight is appreciated!