Can someone help me w/ my lack of conversation ?

There's this girl I am really liking right now , & everytime we are talking on our statuses , over IM or DM , maybe even text eachother there's so much to be said , but when the phones are picked up& we call eachother its total silence I talk but I try not too as much but its still silent I'm scared &im coming as a man I don't what to do I admit I need help . What should I do ? I wanna be everything she needs &provide most of what she needs I'm only 18 . Help .