> I broke up with him before many times because of this same issue but we keep getting back together.

So stop getting back together.

>I feel like he is now taking me for granted because he knows that I'll always be there whenever he returns.

See? You're smarter than you think. You already KNOW how he's manipulating you. Now block him everywhere, and move on with your life. It won't be easy, but you have to break this terribly abusive cycle. This isn't love, this is insanity. You deserve better than this, spend some time trying to figure out why you don't believe that.