Hi CarolV2009,
If I were you I'd get a new doctor. This one is not helping you at all. Three years is a long time.
I had a similar problem. I was told I had unexplained infertility for many years. I actually believed them until I got mad and took matters into my own hands. I started to read everything I could, every spare minute I had.
Early on in my journey I found out I had 9 non-cancerous uterine tumors that would not allow an egg to implant in my uterus. It was an easy surgery, for me at least, and I felt so so much better. I had far less pain and much less bleeding too! Then I learned I had hypothyroidism, when that was controlled with meds I became what people call "normal" for their cycles, I had never experienced this! I felt great! I also had to correct some vitamin issues I had and found out I had allergies to dairy, gluten, and eggs, which were causing my immune system to be in constant overdrive, another possible problem for fertility. I also had low iron, yet another issue that can affect fertilty.
After all this, now I'm finally starting back with my RE and we are all confident my husband and I won't have a problem having a baby this year!
This is only my experience, but what I'm saying is that I have learned (for me) that there is no such thing as "unexplained infertility". It just means I haven't looked hard enough.
Best of luck to you in '09!