Your son was declared on the immigration form and your son's mother was living at separate address and just your girlfriend. Sounds to me like you should be fine. Once you have your PR here in Canada and have enough money saved up, go marry your maganda

Then you can fill out all the spousal visa forms like I did a couple months ago.
It is a long difficult process. My wife's cousin was here for over six years until finally her husband and son finally arrived here a month ago. I am expecting my wife to be here much sooner than that though... 8)