I want it, she doesn't.
Heather Corinna replies:
How will I be able to make love to my girlfriend, because we have talked about it but she didn't agree.
What should I do?
There isn't anything TO do save to wait for when she does also want to have sex with you.
Really, have a think about this. Would you want it any other way?
Who would want to have sex with someone who didn't want to have sex with them just as much? And unless both people really want to, is it really sex? I'll answer that last one for you: it's only sex when both people want to have it, agree to have it without being coerced or nagged, and both are engaged. Anything else and you're talking about rape or sexual assault, not sex.
If you just want to be able to physically express affection for your girlfriend, you can do that without sex. Hugging her, kissing her, holding her hand, snuggling on the couch... things like this are all expressions of physical affection, and when you mean them, they're no less meaningful than genital sex. You two can also get emotionally close without sex, just by talking, sharing things you might not with others, supporting one another in your own dreams and goals, letting one another know how you feel about the other.
If you just need a sexual release, then you can -- and should -- masturbate. When all we need is just to get off, and it's about that more than really being with another person and doing something with another person to express affection and desire between us, then masturbation is what any of us should do, even if we do have a willing partner.
At this point though, if you've voiced to your girlfriend that you're interested in sex, she knows you're interested. If and when she shares that interest, she'll likely say something to you, and I'd suggest waiting until she does. If you keep bringing it up, you're going to be exerting pressure on her to do something she doesn't want to do, and not only is that just not okay, it's likely to create big problems in your relationship.
If you two care about each other, and you love being with her, you can wait, and you'll want to wait, even if you also very much want to have sex. If you two aren't all that close, and you just can't deal with waiting for sex anymore, then you may simply need to be in a relationship with someone else who does share that interest.
Here are a few extra links to round this out for you: