My girlfriend doesn't appreciate me?

So, we're in high school, we've been dating about 7 and a half months and this isn't just some cheesy puppy love sh*t, we actually love each other. I'm always kind to her, and I always show her the utmost respect and care. Usually, she returns the sweetness, but as of a week ago, she is being very distant from me, and she's being very unappreciative. It really hurts and bothers me, that she has to act so moody to me, yet, I'm so nice to her. I give so much, but i get hardly any in return. I care about her so much, I just wish she would me some care nowadays. What should I do? She's usually so amazing, i just don't get her mood lately. :/