That is, they are malformed and cannot swim properly or they have a short lifespan. A normal sperm has a lifespan of about 4 days. Sometimes the problem is the natural decline in fertility that comes with aging, especially after age 40. At first, you will both probably see a primary health care provider. You may then be referred to a specialist.
Men usually see a urologist.
You and your partner will have thorough physical exams. If you have a disorder causing infertility, your health care provider will recommend treatment for it. Sometimes a combination of treatments for both partners is necessary. Taking drugs to stimulate sperm production. Taking an antibiotic to clear up an infection.