What would you do in a rocky marriage?

So my wife whom I have been with for 9 years, drops the bomb that she's unsure of our relationship anymore. We got together when she was 20 and I was 23. After 6 months we moved in together. Sure we had rough times most of which was my fault. We worked through things and I thought it made our relationship stronger. We've been married for almost 4 years and since then she hasn't felt the same. Around that time I did something very terrible and is something that is not easily forgotten. There were some great things that happened for us but thy were tainted by my indiscretions. Now the question. She told me she doesn't know if we are the best for each other. She chats with other men and it makes her wonder about all the what if's in our past. They interest her and she interests them. They make her feel things that I don't or stirs up some deep questions. She said she needs sometime to think about things and get "out of the fog." So she wants to start by getting a job and then "possibly" get her own place. I don't want to lose her but I can't hold her back and change the way she feels, can I? Any input is greatly appreciated. Thank you.