HELP! No positive ovulation test

My husband and I have been TTC for 8 months. I was using the manual Target brand ovulation test strips. I then decided to go with a different brand since we have not gotten pregnant. I used the Clearblue digital, last month, it never gave me a positive for ovulation. I called Clearblue and they sent me anther kit. The test strips from Target do indicate ovulation however we have no gotten pregnant yet so I don't know which kit to trust and I'm very concerned that the Clearblue hasnt detected ovulation at all. Has anyone had this experience before?