Painful ? (TMI)?

I've been ually active for four years and in the beginning, I experienced the normal pain that a newly ually active woman would experience. However, I never got to the pleasurable . Every time I have sex, it is incredibly painful especially at the entrance and it feels almost as though I'm tearing. No matter how much lube is used or how much we have, it is always excruciatingly painful. It's affecting my sex life as well as my husband's and I don't like not being able to enjoy the sex that we do have but every time I go to a doctor, I get the same "nothing appears to be wrong" speech. Occasionally, they'll test me for a yeast infection or treat me with diflucan after making an umption it's yeast, but it has never helped. I just want to know what I can do to increase my quality of sex life.