She's cheated in the past. She could be cheating right, technically you don't know, you're just trying to believe she is better than that and wouldn't want to hurt you. She has one foot out the door.
You've become her "gay" best friend (yes I know you're not gay) instead of the masculine sexual partner she is seeking and maybe currently involved with.
You want to turn this around, do this: - she needs to be home for this to have an effect, after work, go home, shower up, get dressed up, fix up your hair, slick it up, put on the cologne, look like you're going out on a date, if she asks what you're doing or where you're going, tell her "not that it's really any of your business, I'm going out with a girl I recently met" and that's it no more details: no names, no location where you're going or what you're doing and technically you don't have any of those details.
Go out and stay out, don't come home until 2 or 3am.
If she doesn't ask where you're going, don't tell her, just say "bye.", short & simple, nothing more, nothing less. Go find something to do that will keep you out until 2 or 3am. When you come home, be quiet, don't make any noise but go to the bathroom, take a quick shower and then go to bed.
You want her to want you sexually, well up until now, she's always had you and you aren't exciting or sexually attractive, you're you, so you need to start being version 2 of you: someone different, someone who would never do any of this.
And if she ends up wanting you sexually that night or some other night during that week (remember no details on your "date"), don't give in, tell her you're "tired" from your evening and that my friend will drive her crazy.
Currently you want the sex, she knows that, she's in control. When she senses you're moving on and possibly having sex with someone else, she will want to have sex with you, to "tag" you or to "reclaim" her doormat husband, don't give in (no matter how much you want it), just tell her that you don't think it's right, it doesn't feel right anymore. You go from wanting sex to "not" wanting sex with her and she goes from not wanting to have sex with you, to wanting to have sex with you.
Or.... you can continue doing what you're doing and we all know that's working extremely well ;-)
