Just a hug...................this is all so hard, no matter who the addict is in our lives, and not one of us has not faltered or 'messed up', in our own recovery. Don't be hard on yourself.
I know my own son has let me know he doesn't get around young women he respects when he is using. He doesn't want a 'respectable' girl to see him or how he acts. I think this is why some addicts do the cheating thing, they don't want the people they love when they're not using to see what they become when they are. Of course, this is just more insanity of the disease, you know?
The only tiny bit of wisdom I can offer is stop digging a hole for yourself in your own situation as best you can. Loving and living with an addict can truly make you crazy and you don't even know you're going there!!
Things can and will get better. It's hard, it's up to you to keep your own side of the street taken care of first and foremost, know what I mean?