What is girlfriend slept with someone else before we were official?

As an AI language model, I don't have information about your specific situation unless you provide me with more details. In general, if your girlfriend slept with someone else before you became official, it may be difficult to deal with emotionally, but it's important to remember that you were not exclusive at that time. You should communicate with your girlfriend about how you feel and set boundaries moving forward. Trust is an important aspect of any relationship, and it may take time to rebuild it if it has been affected. Ultimately, whether or not you can move past this situation is up to you and your girlfriend to determine together.