First realize, though, that as much as you may want to save your relationship you may not be able to. Make sure that you prepare yourself mentally for any possible outcome. This isn't thinking pessimistically, it is being realistic which is what you need to be.
Make use of family therapy or seek out marriage counselors. They have been well trained and have lots of experience helping people go through these times. Even if there is adultery involved, they will be able to help. Many marriages have been brought back from the edge because of counseling and therapy. They are accustomed to dealing with infidelity between spouses, depression, or any other things that stress a relationship to the point of divorce. Marriage counseling doesn't have to be expensive, there are plenty of good choices for you to use to get good relationship advice before you see a divorce lawyer.
One thing that you can learn not to do that may help stop your divorce before you ever get an attorney involved is don't argue. Arguing will only make the situation worse. You can try calling it reasoning or what ever but the truth is you are trying to force them to feel differently than they do. If you are serious and you want to "stop my divorce" then realize that your battle is against your separation, not your spouse. The more you argue with them and try to point out where they are wrong the more they will be wrong in your mind.
Don't try to defend yourself. You may be right, but don't try to convince them of that. Find the truth in their argument and agree with that. The more you can agree with the things they say, the more they will be right. This will only make them see that you are willing to do what you want them to do, see your side of the story. If you are willing to be honest and accept what they are trying to say then they will more likely be open to listening to your side. Marriage counseling is great at helping you understand how to communicate better if you really want to "stop my divorce."
This is only one part of the things that you can do to help when you are wanting someone to help you "stop my divorce". Quit talking about it and start acting on it. Your marriage will only have a chance to survive if you are willing to act.