I came off my contraceptive pill last month, I had my period from 27/6 to 2/7, after a week I started using the cheap ovulation strips at 4pm everyday, all negatives until yesterday, I used a clear blue ovulation test to confirm and got a smiley face, we had sex last night around midnight and when I checked the ovulation test again today it's negative, is there any chance that we could of conceivd in such a short period of time?