This is a really tough situation. It's important to not rush into any decisions. Try to understand your wife's perspective. She may be confused or vulnerable. However, you also have to protect your own emotional well - being. You could suggest taking a break from each other for a short while to think things through, but during this time, set clear boundaries regarding her contact with her ex - boyfriend.
First, stay calm. Have an open and honest conversation with your wife about your feelings and the situation. Ask her what she really wants and how she feels about you and her ex. If she still loves you and wants to save the marriage, you can consider couple's therapy to work through the issues.