Causes of Low Sperm Count and Fertility 
Low sperm count in men could happen to anyone, even with men with high semen production. Although they can ejaculate a good amount of sperm, the quality of the sperm is not good enough to impregnate your spouse or partner.
There are a lot of reasons why low sperm count happens in men but they could be classified into four:
Health Conditions/Diseases
The following are health conditions that could cause low sperm count:
Sexually transmitted diseases
Mumps
Injury to the spinal cord
UTI (urinary track infection)
Varicose veins (particularly in the testicles)
Overweight and its counterpart, being underweight
Vices – too much alcohol and smoking is not only dangerous to your body to your reproductive performance as well. By causing different health problems, it will eventually affect your sexual performance and foster low sperm count.
Smoking is also a major cause of erectile dysfunction.
Sexual Performance – sometimes, it is also based on your sexual performance. You could be suffering from premature ejaculation or withdraw your penis before you completely deposit your sperm to your partner. Your partner might also be in a menstrual cycle that prohibits her from fertilizing her egg with your sperm.
Work Conditions/Lifestyle – if you’re wearing tight pants all the time or usually in a condition wherein your testicles are exposed to heat, you might have lower sperm count. Radiation will also reduce sperm count as well as use of anti depressants.
You need to prevent those diseases and avoid those certain conditions or situations if you want to your sperm count to be stable. There are also pills in the market that could help you increase the volume of your semen and sperm count. Pills such as VolumePills are known to increase the volume of your semen up to 500%. But you have to remember that preventing low sperm count is always better than curing them.