I'm a guy, and i have the same situation. My gf sneak around to talk to her ex because she knows it upsets me. But he was ****ty to her, and she still talks to him a lot. She's more honest with him than me. The constant not knowing is killing me and this relationship. I don't ever want to tell her not to do something, if she doesn't feel she needs to do it on her own. i can't ever get that right, I feel for you I really do. For the people who say" Just leave them." , thats not even slightly easy when its the only person you have imagined being with for years and you love them enough to die at any moment for them. I'd give up my family for her.
She used to call me when she was unhappy with him, and now I feel its the exact opposite.