How to try to talk to her more often?

[Brenton Pyles]

So I am a freshman in highschool, and have been going out with this girl since October. We used to talk and text everyday, but now it seems to get less and less. I still sit with her at lunch everyday, but I can never think of anything to talk about. She is usually a pretty quiet/shy person, so I don't expect her to start up a lot of conversations. Also her friends have been saying to me that she seems like she is upset with something, and I think she is to. Even though she said she isn't mad at me or upset about something, her texts have been really short answers, her replies to not just me, but everybody have been slightly ignorant and in real life she hasn't talked a lot for the past month.

Any help here?