In English 'coming back' is better expressed as 'returning'. 'coming back home' or 'returning home' does not express the same meaning as 'coming home'.
I think 'coming home' and 'returning home' are in the ordinary course of events. Perhaps one might use 'coming back home' to emphasise the extraordinary return. Although even in the case of the prodigal son it is still a 'return'.
In theory the equivalent of "to come" is "przychodzić", but it doesn't work exactly the same way as in English. For example to us "Are you going with us?" and "Are you coming with us?" are exactly the same thing.
With "I'm coming home" I'd just go with "Wracam do domu", as it is here.