You have a "girlfriend". So now what?!?

Im 15 yrs old in the 10th grade and I have a girlfriend that is 17 yrs old in the 12th grade. We see each other periodically err day. She lives rite beside me and I go over her house multiple times. But things are starting to get boring and the txting has gne horrible. I have text'd her so much and now I dnt know what to tlk abt. I have a feeling the relationship is in a crisis-wat should i do-im frightened???