应该用：I’m very happy indeed.

    【说明】副词 indeed 用于强调形容词或者副词时，总是放在“very + 形容词（副词）”的后面。例如：

      I was very pleased indeed to hear from you. 收到你的来信，我非常感谢。/ He was driving very fast indeed. 他把车开得快极了。/Thank you very much indeed. 不胜感激。（摘自《牛津英语用法指南》第四版）