did the doctor suggest anything to you or that's all he said was "he dont know why you cant get pregnant".
first of all, you need to know when you ovulate. you can buy a ovulation kit at cvs, walgreens, or any pharmacy store. this will highten your changes of getting pregnant.
any problem you have you should research on the internet to find out information and a remedy.
i m going to private message you a few websites, and you should try to research more on your own.