Denis.
Several methods of climbing the mast have been described by other members over the years, but all have involved the use of a secure line to the mast top.
Personally I have made a habit of fitting a stout single-part spare halyard to the starboard side of the mast, and then used that for climbing. If I were you, I would bring a new line, block and shackle (plus twine for securing it) to the mast top next time you go up.
From then on you can use much easier methods, including mountain-climber’s equipment to get up. Personally I use a modified bosun’s chair.
Good luck!
Arne