Hi and welcome to HCM! Thanks for posting your query here. So many conditions affect the fertilization of egg. How about the egg or ovum release? In general it is released from the ovary and is transferred to the uterus. If the egg is not fertilized it results in menstruation. To fertilize the egg a motile and viable sperm is necessary. Female factors like cervical mucus condition, any vaginal infections, vaginal pH will affect the sperm viability within the uterus. Male factors like hypospadias, ejaculated semen volume, sperm count, motile or immotile sperms, the pH of the seminal fluid will determine the fertilizing capacity of the sperm. Timing of intercourse-maximum chances of fertilization in the fertile period and the entry of sperms into the uterine cavity will also determine the fertilization of egg. Please check the conditions what I mentioned above and definitely you will get a clue for the diagnosis. Hope this is helpful to you. Regards