I honestly can't comment on the derma expenses as I've never had any derma treatments (hmm..that explains why
).
I can only say that you are sharing this relationship with her. Thus, if you do not want to proceed into something like desperately having a child nor getting married, then you should be free to say so and discuss it with her. And have you told her that rushing into things like these put you off??? At the end of the day, this story is all about you and your girlfriend. You just have to make yourself clear, I believe. I personally would appreciate a man who has got a voice from the start than someone who would only make himself known after the wedding.