
I'm told that all bitches have a phantom to a greater or lesser degree after every season. With some it's barely noticeable - a little moodiness perhaps - with others going the whole hog, nesting and producing loads of milk. It can be risky to the bitch to spay her at this time due to the increased uterine blood supply and high hormonal activity.
If she was mated at the end of September (you say she came into season in the middle) she would be due to whelp at the end of this month. Why not get her scanned and know for sure?
:)