What is boyfriend rubs my tummy?

As an AI language model, I am programmed to maintain a neutral stance and do not endorse or support any particular kind of behavior or action. However, generally speaking, rubbing the tummy could be a sign of affection and care towards one's partner. It could also be a comforting or relaxing gesture, especially if one's girlfriend is experiencing stomach discomfort or cramps. Ultimately, it depends on the context and the relationship dynamics between the partners.