Sometimes, some women can detect ovulation, but they are not able to get pregnant. This means that the fertilized egg itself is defective, and thus cannot be successfully implanted. Situation 2: Luteal insufficiency of the ovaries If the progesterone secretion in the female body is insufficient, it will lead to abnormal conditions in the endometrium, and these abnormalities will sometimes become factors that affect the fertilization of the egg. Situation 3: Diseases in the female uterus The combination of sperm and egg to form a fertilized egg that cannot be fertilized is probably related to diseases of the female uterus: uterine dysplasia, submucosal fibroids, endometrial polyps, uterine adhesions, endometrial tuberculosis, etc. Situation 4: Immunological infertility If sperm-egg union has been completed, homoimmunity may be the cause that affects the fertilized egg implantation. In other words, the sperm, seminal plasma or fertilized egg is an antigenic substance that is absorbed by the vagina and uterine epithelium and produces antibody substances through an immune reaction, resulting in the inability of the fertilized egg to implant. ”This is what it feels like when a sperm-egg union is in bed Generally, the sperm-egg union is in bed by the 6th-7th day, and bed-entry means that the fertilized egg has reached the uterus. A weak positive test can be detected with a pregnancy test 3-4 days after fertilization (i.e. after the 10th day after ovulation). When the sperm-egg union is successful and the egg implants, first your basal body temperature will drop and some people may experience bleeding. Those who feel sensitive will have aches and pains, and some will have symptoms of a cold. To summarize, there are four things: 1) a drop in basal body temperature 2) a vague ache in the abdomen 3) a feeling of having a cold 4) breast tenderness and nipple tenderness Of course, the sensation of a union will vary from person to person and there is no standard. But usually you will feel more fatigue and loss of appetite, so sometimes even if some of the symptoms may be caused by your own psychological effects, generally it is to the menstrual period after 10 days has not come, you can use the early pregnancy test themselves.