When do you cross the line with a relationship? I have done nothing but forgive and forgive for the…

When do you cross the line with a relationship? I have done nothing but forgive and forgive for the cheating and before we moved back in together it was to stop everything from talking to girls inappropriately to drugs. Still doin drugs and just found craigslist adds he's been replying to and sending nudes to. Why must I always try so hard just to continuously get hurt again. My ring is officially off and I'm not putting it back on after seeing all this stuff.