DB, she DOESN'T avoid thinking about it when she reaches out to you. That's probably why it took her so long to even use the gym membership.
Read the Emotional Intelligence book.
You're really, really not engaging with your work here. You're seriously backward from where you were even a few weeks ago. If you were making progress you wouldn't be so fired up about contact. Find your humility.
Let me put your affair into perspective for you. If I end up divorced and back on the dating scene, I will NEVER knowingly date ANY cheater. Even if he never cheated on me. I just will absolutely not go there. I'm quite sure I'm not alone in feeling that way, and not only among betrayed partners. So when you cheated on your fiancee, you didn't just pollute yourself for her, you polluted yourself for a whole class of women who think too highly of themselves to put themselves in the position where they COULD be cheated on.
That's the scale of your transgression.
Now, quit thinking about your ex, do the work and be better.
Me42, H40 D12, S8, S7 A revealed: 7/13 Sep 4/14; Agreed to D 1/15