I agree that cd 4 would be way to soon to ovulate. My RE doesn't even have me start testing until CD9 or 10. Good Luck with your ultrasound on Friday!
I highly doubt the positive on cd4 was a true positive - I know I remember reading somewhere that clomid can cause you to get a false positive opk if you start testing too early. I think you are supposed to ovulate like 4 or 5 days after the last clomid pill, so keep testing with opks because I bet you have yet to ovulate! Good luck! I myself am on my first round of clomid and I'm praying that it makes me ovulate!!