Suggest Treatment For Infertility

i am 30 years old. i got married 14 months ago. my wife age is 23 years old. i did planning to child birth about 10 to 11 months after that we planned to get child so we have tried 3 to 4 times on most fertile period of my wife as she is having regular period schedule but she get let when we got sex on fertile period And she don't get pregnant. we are so worry about that and don't understand why do not she get pregnant. Hep me.

Thanks