It's years (since) I enjoyed myself so much.Why?

It's years (since) I enjoyed myself so much.Why? it is years since i enjoyed myself so much it 's years ______ i enjoyed myself so much it's years since i enjoyed myself so much.中文意思是否为：我已经好多年没这么开 It has been many years since I enjoyed myself so much. It's years when I enjoyed myself so much.翻译,并解释这里when的用法 It is years since I enjoy myself so much It is been years _________ I enjoyed myself so much as last It's years since l enjoy myself so much.since可否换成before? It was years since I ___________ (enjoy) myself so much.填什么, it's years since i I enjoyed myself very much last night .