Is "so do I" or "so I'm I" a natural and common answer?

Question

Is "so do I" or "so I'm I"  a natural and common answer?

Answer

I have met SURE DO I.

Answer

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."

Answer

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

Answer

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