How can I explain to my girlfriend the importance of being sexual?

Me and my girlfriend of 2 years have been sexual active for a year and a half now. We both believe in sex after marriage so we just do everything else but have sex. But my question is how can I explain to her the importance of sexuality in a relationship? Every time I try and tell her about it she thinks it's a bunch of lies and I'm just trying to get some. But its not true it's so much more than that it's that deeper bond and the feeling of how I'm the only person she's ever done this with and me with her. It's so deep and complex and if we go long periods of time without it I start to feel like depressed and than my mood starts to change in a bad way. Being sexual means a lot to me it does to her too but she also doesn't need it like I do so she doesn't know how I'm feeling anything you guys can come up with would be great just in a non "I just want some ***" kinda way...because that's not true