I have met SURE DO I.

When you want to say that something is the same for you or someone else, you put the verb before the subject. "I wake up early every morning." "So do I." "So does he." "So do they." "I'm very sick." "So am I." "So is she." "So are they." "I have been to England." "So have I." "So has he." "So have they." If the statement you're agreeing with is negative, you need to use "neither" to agree with it: "I don't wake up early." "Neither do I." "I'm not sick." "Neither am I." "I haven't been to England." "Neither have I."

Did you perhaps mean 'so am I'? That is also natural and common.

so do i is commonly used, to mean that you agree. For example - "I normally eat breakfast at 8am", "So do i" SO I'M I would not be used at all, it's not grammatically correct