Girls love to keep guys "on the hook". I haven't met a single girl yet who doesn't subconsciously do this. OP needs to make his feelings absolutely clear, it's out of line, BUT there is an element of mistrust on his side I think. They will have to come to a compromise - children with an ex ALWAYS make things especially awkward.

Sorry for the judgement of OPs gender!

Edit: woo downvotes! 