I replied to your other post the other day. As I mentioned, it is normal for the uterus to be open as it opens and contracts during your periods. Over time, it contracts less and less. Especially if you have had children. I am guessing that birth control might possibly have an effect on the amount of contraction? I am not sure. Even though it is normal for the uterus to be open... there may be a limit to how far open is actually normal and ok. Again, I am not sure. Just a theory. It may be affecting your cycles. I still think your best bet might be to see a second doctor just to be sure that you are getting the right treatment (since you have doubts). I personally can't really offer much more help. I tried to do some research on the matter and didn't come up with much and if it was out there, I am usually pretty good at finding it.
Still, keep an eye out because someone mught come across this post that knows more then we do. If you do find out any info, would you please share it with everyone so it will be here for the next person that has to deal with this? Thanks!