Many years ago I was trapped in a similar relationship. A young woman I was madly in love with and wanted to marry kept flipping between myself and another boyfriend. After a number of years of this , hoping she would chose to be with me , I let her know that if she was to flip back to the other guy again that it would be the last time. She did flip back and right on schedule , 6 months later , she was looking to come back. I declined as promised. I could find out what happened to her but I decided long ago to "let sleeping dogs lay".
The only one in control of your life... is you.