I can't be honest about how I'm really doing
Why can't you be honest about how you're doing ?
I'm unhappy in my relationship because my partner isn't doing what I want her to do.
Sometimes it can be hard to articulate our grievances with our partner, but if there's something in your relationship that is making you unhappy then it's important to talk about it. If you're not honest with your partner, then they aren't going to be able to make the necessary changes to fix the relationship.
I can't be honest. My partner is going to find out that I'm cheating on him.
So you're laying all the blame on your partner for your own bad behaviour. There is no excuse to cheat on your gf. If you're so unhappy with the relationship, you should break up with her.