There are a number of things that may be keeping you from getting pregnant:
Damage to your fallopian tubes. These structures carry eggs from your ovaries, which produce eggs, to the uterus, where the baby develops. They can get damaged when scars form after pelvic infections, endometriosis, and pelvic surgery. That can prevent sperm from reaching an egg.
Hormonal problems. You may not be getting pregnant because your body isn't going through the usual hormone changes that lead to the release of an egg from the ovary and the thickening of the lining of the uterus.
Cervical issues. Some women have a condition that prevents sperm from passing through the cervical canal.
Uterine trouble. You may have polyps and fibroids that interfere with getting pregnant. Uterine polyps and fibroids happen when too many cells grow in the endometrial, the lining of the uterus.
" unexplained" infertility. For about 20% of couples who have infertility problems, the exact causes are never pinpointed.