My girlfriend is not comfortable around me

Me(20) and my girlfriend(19) have been together for 4 months and we knew each other for one year.
She looks bored when she talks to me.
I recently started “touching” her more (holding her by her waist and things like this) and she seemed to like it.
If I ask her when is she free to hang out she says “I don’t know,I will tell you” and usually never brings this up again.
We now only see each other at school and when we talk staying side by side she doesn’t look at me,she fidgets a lot and seems bored,as if she was bored by me.
When she talks to other guys she is all excited and watches them in their eyes.She never initiated touch with me but she did with other guys.
To me she seems uninterested.
She seemed all excited to talk to me through messages and until yesterday she told me goodnight and that she loves me everynight,yesterday she seemed uninsterested even via messages.
I don’t know what to do,she has closed body language around me and sometimes I feel like she ignores me.
What should I do?Discuss or pull away as well?

Thank you in advance!