What Phil is telling you is important, you cannot have a 14 awg (15a only) wire on a 20A circuit breaker, it will eventually burn out your wire & possibly your receptacle. so you must address that by ugrading your wire to 12awg which is good for 15-20A.You should have the gfci in the bathroom outlet circuit, but you don't need it in the office., maybe you should consider a different tap for the office recept. try the lighting circuit in the office space and see where it leads, what else is connected to it & how many amps available from breaker panel.
For The Extension Outlets: You can use metal/or plastic raceway (Bower,Wiremold or Panduit) they have extension boxes for the excisting outlet box and you can branch off to other outlet boxes with raceway and add as many receptacles as needed along the run. if you use the plastic type, include a grounding wire (3rd wire) from the originaing box to your receptacles.
But it is important to do something about the 14/2 cable you installed. it is not proper by code for the circuit plans you have and may pose a hazard if loaded beyond 15 amps, your breaker wil not trip while the wire is rated to carry only about 15amps., It may heat up and melt or burn before the CB trip ~ after >20amps has been compromised., if you plan on leaving it (which is a code violation) make sure you do not add up anything more than 15 amps in office equipment. Change it and through caution to the wind };-)
=AEoy