To say how long you have been doing your job or your studies, Spanish uses the PRESENT tense, not a past one: "llevo" + a length of time + a verb ending in -ando/-iendo. The equivalent pattern is present tense + "desde hace" + the length of time. Ask about it with "¿Cuánto tiempo llevas...?"
Examples
- Llevo tres años trabajando de programadora en una empresa pequeña.
- I've been working as a programmer at a small company for three years.
- ¿Cuánto tiempo llevas estudiando Derecho?
- How long have you been studying law?
- Trabajo en esta empresa desde hace seis meses.
- I've been working at this company for six months.
- Llevamos dos meses buscando un contrato indefinido.
- We've been looking for a permanent contract for two months.
The mistake to avoid
Don't copy the English perfect - "he trabajado aquí tres años" sounds finished; say "llevo tres años trabajando aquí" or "trabajo aquí desde hace tres años" for something still going on.
Where this fits in
Work & study, Spanish B1: Discuss your job, your studies, and share opinions about working life using comparatives and opinion verbs.