I want you to know that I went through the same thing for many many years, and it was even worse because I had a child with my ex. I wondered if ever, and even still today, the Lord was going to relieve me from having to deal with this issue.
First and foremost Bett, please make sure your local police department is fully aware, and if you haven't already, get a protective/restraining order against him.
Now, I can tell you that even though you don't feel it, the Lord is covering you. This experience is going to teach you to trust Him like never before. I know it is miserable, and I know it seems like evil is prevailing, but IT IS NOT! Trust Him through it all.
You need to walk the perimeter of your property and read out loud Psalm 91 or any of the other Psalms that talk about our protection -- consider one of those written by David as his life was constantly pursued. You need to anoint your house with oil, covering every window and door, and plead the blood of Jesus over it. Evil cannot cross these boundaries!
And finally, you will make it through it all. The Lord is not happy with this person stalking His child. The Lord will deal with this in His time. You have to trust Him and believe in your heart that He will protect you. This may be one of the crosses you have to bear right now. Thank Jesus and worship Him in the midst of it all, and watch Him move on your behalf.
I can speak from experience after 17 years of the same thing. Things are a little better now, but for the first 12 years or so, it was absolutely miserable, and I often feared for my life and felt like things would never change. They did though, and I and my child have remained unharmed for the most part.
Be strong in the Lord, for you can do all things through Him!