Well..to state the obvious. If things are boring it's probably because you are stuck in a rut. Make an effort to change things. Suggest doing something you don't normally do together, go somewhere different, take a weekend break somewhere or take some time to yourself.
Things are becoming boring because you are both letting them, maybe have a casual chat about whether you both feel things are a bit stale. He may feel things are comfy and you might be bored. If you talk to him then at least both of you can acknowledge the problem and both contribute to keeping the relationship fresh.