How Do I Tell If My Gf Is Tired Of Me?

It sounds like your girlfriend has a change of heart.  You should sit down and have a talk with her.  Ask her what she really thinks and how she feels about the relationship and be honest.  People are afraid of confrontations because they are afraid to hear the truth or what might be coming.  You should prep yourself that she might want a break up.  
But when breaking up is never easy but from the sound of it you are still young and dating around is a very good option. I think before people settle down they should date as many people as they can or a decent amount that could allow them to make the right decision by comparing and find out what type of woman or men suits them. I would not try to reconcile if she decides to date someone else.  Always keep your options open because if you and her are meant to be together, it will happen.  And i get the feeling that maybe she is doing all this so you can bring it up to her first and maybe  be the one to break up with her.

Well, well, well. I was thinking that you should just go right out and ask her about it, I mean if she feels that you two have grown apart than maybe it's best that you split and go your separate ways- because in the long run if your just staying together for the 'routine' then you are both going to miss out on the 'fun' that you could be out there having.