How can i find out how fertile i am?

You cannot: The tests used to determine the cause of a couples infertility are generally only valid in people who actually have infertility. The only way to figure out if you have infertility is to try to conceive and not be successful.

Two ways: 1) become pregnant, 2) see a doctor. There are many causes, categories, and sub-categories of female fertility problems: clinical history, timed blood work, and imaging studies are needed. Sometimes surgery is a diagnostic option as well. I also remind that 40% of women who don't conceive are fertile but the male partners have problems. Good luck.