Am I being a selfish friend?

My friend and I text a lot. Recently, she's been trying to get into a relationship.

She talks about boys a lot and goes on about how lonely she is, and that she can't wait on finding someone.

I have a steady boyfriend, my first, and we've been dating awhile. The problem is, thats about as far as my relationship experience goes.

So when she says these things, I have no clue what to say, and try to lighten the mood or change the subject. She complains I don't take her seriously and that she feels like I'm making fun of her. However, I really just don't know what to say do to lack of experience, and have told her that.

Of course I don't do those things, and I'm sad she's upset, to the point where I never talk about my own relationship. But I feel like thats all she ever wants to talk about and I'm a little sick of it. Am I bad to say that?

I really want to support her, but it's hard to hear about only the same few things all the time, and our conversations are nearly always one-sided. I have to fight to talk about what I want to. I've brought it up before, a bit more delicately, but nothing's changed.

Am I being selfish for getting to the point where I just don't wanna hear anymore? Am I not supportive?