Do you know what day is June 15? It's World Infertility Day.

Infertility is defined as not being able to get pregnant despite having frequent, unprotected sex for at least a year for most couples. Infertility may result from an issue with either you or your partner or a combination of factors that interfere with pregnancy.

But there is another type of infertility that isn't discussed very often and that's secondary infertility. The inability to conceive or have a full-term pregnancy after having had children without difficulty before is the definition of secondary infertility.

I experienced secondary infertility. I had my son when I was 23 years old, and I waited four years to try and get pregnant, figuring it would be easy. It was easy to get pregnant but after five weeks I lost the baby. It was devastating, something that I hoped to never experience again.

I was told by my doctor to wait three months before trying again. We tried again and I quickly got pregnant again, but five weeks in, I again lost the baby. Going to the doctor, looking for that heartbeat and not seeing it at all. The first time was devastating but the second time, I felt like a failure.

What did I do wrong? Why can't I stay pregnant?

My doctor sent the baby off for genetic testing to try and figure out what caused my miscarriages. The results were stunning, for some reason my body stopped producing progesterone after the fourth week. What's progesterone?

All women who wish to become pregnant need progesterone to help the uterus prepare for and maintain a fertilized egg. After ovulation occurs, the ovaries start to produce progesterone needed by the uterus. Progesterone causes the uterine lining or endometrium to thicken. This helps prepare a supportive environment in your uterus for a fertilized egg.

A supply of progesterone to the endometrium continues to be important during pregnancy. Following a successful implantation, progesterone helps maintain a supportive environment for the developing fetus. After 8 to 10 weeks of pregnancy, the placenta takes over progesterone production from the ovaries and substantially increases progesterone production.

But, my infertility didn't stop there, once the doctor figured out the progesterone situation, I should have been able to get pregnant. It didn't happen that way, after more testing, it was determined that I was no longer ovulating. So the next step was I took the fertility treatment, Clomid.

Clomid is an ovulatory stimulating drug used to help women who have problems with ovulation. It is the most commonly used fertility drug. Clomid can be prescribed by a gynecologist and doesn't require a fertility specialist, it's also the very first fertility treatment tried for most couples. Clomid is taken as a pill. This is unlike the stronger fertility drugs, which require injection. Clomid is also very effective, stimulating ovulation 80 percent of the time.

I had two treatments of Clomid and was lucky enough to get pregnant, as soon as I found out I was pregnant I began taking the medication progesterone until I was 12 weeks along. During that period I also was visiting the doctor for weekly sonograms to keep track of the baby's progress.

November 13, 2001, I gave birth to my second child, a daughter, almost three years after my journey began. This journey was one of the hardest journeys I traveled, even though my husband was there, it was my suffering, my body, and my loss. I don't think he could comprehend the amount of hurt that I suffered the loss of my two babies and the fertility treatments that I endured.

According to the National Survey of Family Growth, more than 1 million couples grapple with secondary infertility. The most common explanations are these: A previously fertile partner is trying to have a child with a new spouse, or one or both partners in an existing relationship have developed fertility problems since their last child was conceived.

A woman might have developed endometriosis (one of the most frequent causes of secondary infertility in women), irregular ovulation, or fallopian tube disease. A man might have had a decline in the concentration or motility of his sperm.

The factors can involve age (even five years can make a big difference in a woman's fertility cycle and a man's sperm count), scarring after childbirth, or stress, which can affect ovulation and sperm production.

Some couples, like I was, are shocked when they are unable to conceive a second child, especially if they became pregnant easily, or accidentally, the first time. Secondary infertility can cause stress, sadness, frustration, and loss for many couples.