Well ,you don't have a child means you and your wife needs to be investigated. You have low sperm motility
.I would first like to know whether you have any habits of smoking
or alcohol,then please quit as these are proven to decrease sperm motility.Secondly if you have got any varicoceles as evident by swollen cord like structures in your scrotum
please consult a doctor. As regards to diet please take healthy diet with fruits -these contain antioxidants
.Prepartions containing CoQ, astaxanthin and antioxidants available in the market can help. Plese avoid exposure to hot environment continuously.