Problem in Conceiving. Something wrong?

Hi. I'm married for 2 years, and we are trying for children from last June. In June, my periods got delayed by 5 days, when I actually thought I had conceived. I had sore sensation in my breasts those days, and I was pretty confident that I'm Pregnant. That was the first time my periods got delayed (usually its 0-2 days, mine is 29 day cycle). Since then we are trying almost every month from 13th to 17th day after my period. During these days, I get the symptoms of ovulation similar to PMS , so I assume that I'm actually ovulating on those days. We have sex every alternate days/every day on those days(only after 10 PM). Every month I'm only disappointed to see me getting periods. What can be wrong? Are we doing something wrong?