What I'm doing next ... taking a lot of medication (9)

'what i'm' is the definition.
I can't tell whether this definition defines the answer.

'doing next taking a lot of medication' is the wordplay.
'doing next' becomes 'coming' ('come' can be a synonym of 'do'. I am not sure about the 'next' bit.).
'taking' means one lot of letters goes inside another.
'a lot of' means to remove the last letter (a lot of but not all of the word).
'medication' becomes 'pill' (pill is a kind of medication).
'pill' with its final letter taken away is 'pil'.
'coming' going around 'pil' is 'COMPILING'.

Can you help me to learn more?