ok, so your 'in love' with your girlfriend?
if you don't want to fall in love with her because your afraid of getting hurt, things may not work out and your be left with heartache, then your not alone! we all go through it sometime in our life! I believe this is just an insecurity will feel about our future. Don't dwell on it, just enjoy it, relationships are suppose to make your life better, not worse, so if it's making your life worse then it's not for you. if it is, then what's the problem?
it's not bad to feel for someone, it's good! try not to let it become and obsession though, go out with your friends, work at any hobbies you may have etc... but still have time alone with your girlfriend.
don't dwell on bad things, just enjoy the time you have with her! we only get one life, why waste it by focusing on NEGATIVE emotions! your the man!