My husband cheated on my for so many years and finally after 20 plus years I left. We were still talking and I was trying to get him to go for counselling because he wanted to try and make it work. Then I found out that he had a girlfriend the whole time that stemmed from before I even left. Now, the only bills in the house are in my name and I kept my stuff in the house because I didn't want anything eliminating my chances to reoccupy the house if I wanted or needed to come home and live. I recently drove to my house to check on things and I found her stuff throughout my yard and some in the house. I wrote her a message on fb giving her 24 hours to remove her things from my home. Then I called him a few hours later and politely asked him what was going on. He told me that he moved her into our house and threatened to have the cops after me if I go there at all. He stated that it isn't my house at all and that it belongs to him and our young son. But my name is written right beside his on the deed (which I possess). I know property laws are different depending on where you are. I am located in Ontario, Canada

You can't force the GF out as long as the other co-owner and current resident says she can stay. Likewise, since you are a co-owner he can not call the cops on you for trespassing. Your goal at this point should be to file for divorce, so you can get your portion of the value of the house (and other marital assets) and move on with your life.

Until you file divorce papers and the judge orders her and your husband out of the house You cannot just order her out of the house. File for a divorce and get the house back or have the judge order it sold and you get your portion of the home sale awarded to you.

Hate to say that but technically when you left you gave hubby the green light to move his girlfriend in. You could come back and he could do nothing like calling the oops as your name is on the house also and the cops could not legally remove you from the house. But why would you want to go back under those circumstances?

Consult with a good divorce attorney as soon as possible.

but my name is written right beside his on the deed (which i possess). i know property laws are different depending on where you are. i am located in Ontario, Canada

Property laws aren't that different. But we would have to know how the deed is worded. But if you are listed as a joint owner and the deed you have a copy of is the currently recorded one, then you are a part owner. And the previous answers are correct that he can't have you arrested for trespassing, nor can you have the girlfriend removed.

But you also made a big mistake by posting on Facebook as you did.

So your best bet is, as has been advised, to consult with a divorce attorney immediately.

Facebook gets more people INTO trouble I've noticed.