I am27 year old and i am creating sex with my wife 3 months but she don't get pregnant why ?

Conception: The best time to conceive is usually around the ovulation date. Let us use a cycle days of 28 days as an example. The estimated ovulation date is 28days -14days= 14days. Kindly remember that spermatozoa live about 5 to 7 days in the womb. Thus, it is likely to conceive when sexual intercourse occur from cycle days from 9 to 14. Good Luck.