I don’t think Cora would have made Regina infertile. If anything, had Regina had Leopold’s child, especially if it was a son, it would have secured Regina’s place as queen and meant that her child was an heir to Leopold’s kingdom. If it was a boy, it would have skipped ahead of Snow and been next in line for the throne. Cora would have loved that.
I don’t think Regina and Leopold did sleep in the same bed. Regina had her own separate chambers and Leopold locked her in there when he thought she was having an affair. It is possible that Leopold and Regina may have slept together once on their wedding night in order to consummate the marriage but there is no guarantee Regina would have gotten pregnant from that. Leopold still loved Eva and was only looking for a mother for Snow. Except for the marriage consummation, I doubt Leopold touched Regina in that way.
As for Regina not being pregnant in Storybrooke, the time loop may be a part of it, but could it also be the fact that Regina never wanted to be pregnant, she just wanted the end result of a child. Considering the evil queen’s main trait in the original Snow White tale was her vanity, it makes sense that Regina wouldn’t want to go through all the morning sickness, bloating and increasing in size that pregnancy entails. Adoption was ideal for her.
As for her comment to Owen, children are often seen as a sign of love between a couple. Daniel was killed before Regina and him could get down to it, so it’s possible that had Daniel lived, he and Regina may have had several children together. Regina and Leopold was a loveless marriage, he probably didn’t touch her beyond the initial marriage consummation. Regina was there for show and to be a mother to Snow. Nothing more. Regina was aware that Graham didn’t really love her, so she probably didn’t want to bring a child up in a loveless relationship which is essentially what Cora did with her and the last thing Regina wanted was to turn into her mother.
All magic comes with a price!
Keeper of Felix