DM did it over a period of 3 years I think
to come back to the OP's post
to do the Camino in one stretch is a big ask - that's just under 30km a day across mixed terrain, none of which is particulalry flat, and in temperatures that can be well into the 30's in summer. being gym fit is one thing - being fit to do this is another altogether.
how much walking do you do at the moment? if you're an experienced walker comfortable with a backpack for long days in the hills, then I'd say fine - it's doable. but I just suspect you're too inexperienced at this stage to do it in one go.
it's a good challenge but I think you might need to do a bit of joined up thinking first