What Causes Inability To Conceive Despite Having Normal Hysterogram?

Hi, I have been trying to concieve.i have regular 31 day cycle.Last month I had soon hysterogram on 6 th day of my menstrual cycle.its saline water that was passed into my tubes and they were patent.Assuming that I ovulated on 18 th day, we were together on every 4 th day from 12th to 20 th day.but still I didn t concieve and more over I had severe cramps and somewhat heavy bleeding compared to other cycles.Why didn t I concieve? Does the tube test has to do anything with this?