Ever thought that maybe its not you?
Maybe your husband has a low sperm count, if he smokes wears tight underwear or drinks or does mild drugs.. All of these could affect it. Even if he has a hot bath every morning can decrease a sperm count.
There are vitamins that you can take that will help with it, I had a friend who could not convieve for over 2 years, she started takign these vitamins.. And a few months later she was pregnant.
Usually after a set amoutn of time you are aplipical to ask for assisted concecption I believe btu it depends on your country and state!
Best of luck