Having with my girlfriend..... (bit of a complicated one)?

I have been seeing this girl for a few months now and I feel we're ready for and I think that she would be ok with it too (we've discussed it before, and we have been physical with eachother to a certain point on several occasions in my room). The problem is that I think she has more of an emotional attachment than I do and I may not want this relationship to continue for an indefinite amount of time. I may just want it to last for a few months. I don't have a lot of experience with women either, so it's new ground for me. I realize that all of you are going to say that I need to be in a committed and honest relationship before we do anything, and we are. Just I have not shared with her that I may not feel as strongly about her as she does me. I have not mislead her in any way, but I am worried that I may hurt her feelings in the future. When we talk about I get the feeling that she is someone who wants a deep commitment before having , but I think she would have with me if I were to bring up the topic. I just can't give that commitment to her, but I do want to have . What are my options? Try my best not to hurt her, wait.......(please don't say this one lol), or tell her now that I don't think it's going to work? I'm very confused how to approach this situation. She really feels im a great guy, and I try my best to treat her right. I don't want to take advantage of her either.