you're so doing this 是什麼意思?

You’re so doing this.
先参考一句英語母語人士的類似句子及解釋
The patient is doing so well! It's hard to believe he is doomed
to die in a few days.
現在進行式意味為現在，之前沒，之後也沒，“so” 有強調及到此為止意味。
該句 (… doing so well)句基本上無進一步解釋，其真正意思不明。
It always seems to demand an explanation to know which way
things will turn....for the better or the worse/the worst. - 英文原句解釋
You are doing so well! If you persevere, you might even get a
scholarship. – 英文解釋例句.
所以說基本上You’re so doing this. 即使this 改為well也不見得就是一句正面樂觀的話 – 有點像你現在終於知道要這樣做的感覺

你為什麽是這麽做?
=so that is how,so it is how you're doing this.
so=adv of manner "in this way"