Dear Anne,
There are several factors which could be involved in your inability to conceive thus far. The first, age, is not alterable.
The spotting may indicate that you have suboptimal levels of progesterone in the luteal phase since days 23 and 26 are post-ovulatory days. Low progesterone can also cause premenstrual spotting, three days or more of spotting or very light bleeding that occurs right before the next menstrual flow as well as tail-end brown spotting. Tail-end brown is brown colored spotting that occurs at the end of the menstrual flow.
The IUD may have provoked a chronic inflammation of the lining of the uterus called endometritis. This condition can also cause premenstrual spotting and tail-end brown.
In general, about 90% of couples of normal fertility should conceive within six months of starting fertility focused intercourse. Fertility focused intercourse means couples use NFP models or fertility monitors to determine their fertile days and then have relations on those days.
In your case, since you have some abnormalities already evident, I suggest you find a medical professional trained in NaProTECHNOLOGY so that you can start an evaluation. Go to fertilitycare.org to find a practitioner to teach you the Creighton Model of Fertility Care and to recommend a NaProTECHNOLOGY medical professional.
In health,
George Delgado, M.D.
Natural Family Planning Medical Consultant