You haven't said whether or not you find women sexually attractive. If you don't feel desire for women, I believe you may be mixing up strong feelings for this girl with romantic love. You also did not say what her sexaul preferences are. Does she say she is bisexual, lesbian or straight? Lastly, I wonder why it important for you to have a label. Will things be any better if you have one sexual preference as opposed to another? Has this girl asked you what your sexual preference is? If so, she certainly has the right to know, especially if she is planning a life with you.
I don't believe that you HAVE TO have sex with a man and a woman to know which one you prefer or if you like both. There are plenty of straight people that are confident in their sexual persuasion without having to try the same sex and vice versa with gay people. You can certainly experiment if you like but I don't believe this is a necessity.
You know yourself better than anyone so only you can answer this question. Look inside yourself, be honest about your sexual and romantic feelings about both sexes and you will find the answer to your question.

thanxs. well she's a lesbian. and i kno i like girls. i love her. n its true,i shouldnt label what i am. and i shouldnt worry bout sex wht a guy. im jus afraid cause its long distance,n we havnt met. we're both 17 with not car or job. thank you for taking the time to answer me.

I say just go with bi.. a friend of mine just considers herself that.. she finds guys goregous but intimately she prefers girls..she never had sex with a guy but fooled around with one and was well grossed out by it all.

my advice is has the g/f visit first.. see how compatible you are in person and sexually.

i think you need to figure that out before you say you plan on marrying a women. it wouldnt be fair if you get into it and then change your mind, which will turn her world upside down.
you do know what she looks like?