Originally Posted by groovy9
Take it from someone who's been cheated on: Don't. It's a miserable experience for everyone involved.
Suggest an open relationship if you think there's a chance she'll genuinely go for it. If there's a chance counseling will solve your problems, knock yourself out. Otherwise, just leave. She doesn't deserve to be lied to and you won't enjoy doing the lying.
Besides, even if you cheat and she finds out and doesn't leave, it certainly won't improve your home life and you'll just end up spending more and more time with someone else until you finally do decide to leave.
Take it from the person who has done the cheating...it scars you and if you know better (which you do) avoid it at all costs. Better off to leave her in my opinion.
If you are at the breaking point then say something, ask for an open relationship or whatever but don't cheat. You can't undo it.