What is wrong with me?

I've been ttc for 2 years on and off. I would get hopeful be disappointed and give up for a fee months, but this time around been trying for 6 months strong. I missed AF in August and I tested only to get a negative. I'm now supposed to be in the middle of ovulation again and still no AF. It's due to come again Sept. 9 . I'm confused and would like some advice on what is wrong with me.