<human>: Summarize the given text in a few sentences.

I am an active Reddit user who hasn't posted here, but I am desperate for help.

I am in a relationship with a partner I love very much. It's been two years. We've had our ups and downs, but have always been honest with each other. I have always been honest.

But during one of our "downs," a coworker of mine started flirting with me. And I flirted back. We texted, we met, and occasionally "sexted," although no pictures were ever sent or received. She would send me a sexual message, and I would send back, in FEAR that if I didn't comply, she would tell my girlfriend about the flirting.

I know, it doesn't sound logical, but I struggle with some mental health issues.

Anyways, the coworker wanted to make it physical, but I refused every time. I've NEVER touched this girl, not even as much as a hug. I ended it (although she kept manipulating me) and it created a web of lies. All of this, obviously, has been hidden from my loving girlfriend.

Now, of course, I have never been more in love with my girlfriend. We are in one of our biggest "ups," but my mind has deteriorated. i am overwhelmed with extreme guilt. Nauseating guilt. It has ruined several days for me. Even though I try to tell myself that I didn't cheat and that nothing I did was too bad, besides the lying.

Is this a relationship problem or a mental health problem? Should I tell my girlfriend about this? (She also struggles mentally and I don't want it to ruin her life with obsessive thoughts like it has done to me.)

Please give me direction. I'm afraid that if I tell her, it will make her life more difficult over something that might not even need to be said. What would you do?
<bot>: I flirted with a coworker for one week, and because of my initial mistake, I have been lying ever since to get out of it. Should I tell my girlfriend? No physical contact made.