Endometrial polyps

I was just diagnosed with Endometrial polyps, I also have a 3 cm Ovarian (simple) cyst on my left ovary.  

They actually found the Polyps during a Endometrial Biopsy which was done due to spotting after intercourse.  My pap smears have always come back normal.  Does it seem odd that they didn't detect the Polyps during the Transvaginal Ultrasound?  Isn't this the way they are normally detected?  

My doctor is scheduling me to have a D&C in a few months ..  she said there is no rush, but will need to be done to make sure all the Polyps are removed.  

Thanks for your Help!

[Nymariarya]

When I had my trans-vag ultrasound, I was informed that since polyps are softer in nature than fibroids that they are often undetectable by ultrasound.  Since no fibroids were found on that initial scan, I was scheduled for a saline-infusion sonohysterography & endo biopsy. They had a difficult time infusing the saline and suspected I simply had clots and adenymyosis since I was bleeding at the time. My polyps were confirmed by the biopsy, not by either ultrasound.