Most of us spend so much time trying not to get pregnant that we expect it to happen immediately when we’re ready got start a family. But for about 12% of American women, pregnancy doesn’t happen so easily. And the infertility problem is on the rise: Nearly 40% more women report difficulty getting pregnant than 30 years ago.  Why? No one really knows. In 2011, the American College of Obstetricians and Gynecologists, attributed many cases of infertility to disease, lifestyle and congenital factors, but could identify no specific cause for infertility in 20% of couples. In the past, I’ve written about studies showing links between female infertility and non-stick chemicals. But…