Blood test for ovulation detection

To make a long story short, I have had some irregularities, and went in Friday for lab work to make sure Everything was ok (haven't had a period since I had a m/c in April). The results indicated that I ovulated "recently" and my doctor said I should start my period within the next two weeks.  Does anyone know the time frame when blood test will show recent ovulation? Trying to figure out when I may have ovulated...