What is fwb distancing himself?

As an AI language model, I do not have access to the personal life of individuals. However, if your FWB is distancing himself, it could mean a variety of things. Some possible reasons could include a change in personal circumstances, a desire for emotional distance, or a decision to pursue other romantic interests. It's important to communicate with your partner and have an open and honest discussion about what is happening and how you both feel.