Thanks again for your words
I think I can use them to change myself a little at least for the sake of my girlfriend.
We spent the weekend together and I actually confronted her with my feelings, that I feel she has no time for me and all. She doesn't feel that way at all and she made it clear to me: she always calls me after school (even though it might be for just a few minutes), she always asks me how I feel and so on.
I guess she's right and maybe I want to much, and it's probably because I don't have anything to do the whole day so I just sit around doing nothing while she has lots of work to do.
Angela: thx, I will try that
Christian: thx, I will try that
Jim: thx, you're right