What Causes The Inability To Produce Child?

Hi My wife and I have been trying for a baby for approximately 1 year, with no success. Last christmas she told me she had sore breasts and cramping (approximately 2 weeks after a missed period). About a week later she had very heavy bleeding which she described as bitty . After this she missed the next two months cycles. My wife is 5ft 5, with a bmi of 33 to 34 and has irregular cycles - sometimes she has a 22 day cycle, sometimes it can be over 40 days. She has had routine blood tests which have highlighted nothing wrong with her hormone levels and she has had a ultrasound scan of her insides after which she was told she has all the right equipment to make a baby. I visited our doctor with her and he has sent me for a sperm test. I am very nervous about it, there is no history of infertility or any form of genetic problems in my family. I m a healthy man, 6ft tall weighing 12 stone 6lbs. I produced the sperm sample yesterday, it was 5ml, cloudy grey coloured. Does someone have a suggestion what could be going on?