Greetings, welcome to the Forums.
When does your fig leaf out in Spring and drop leaves in the Fall?
Does your tree still experience cool/cold temperatures indoors in Winter?
If it is not getting taller, is the new growth coming from the base of the plant?
If possible, please post a pic of your plant.
The Mediterranean Edible Fig (Ficus carica) is a temperate, deciduous tree, that would usually do best outdoors. Brown Turkey Fig (Ficus carica 'Brown Turkey') is certainly cold hardy enough to be kept outside in Portland year-round. However, it is a worthwhile experiment to try growing it indoors.
Edible figs do well in containers, though like all woody plants they will eventually need to be 1) potted up, 2) planted in the ground, or 3) root-pruned ever few years. Root-pruning is best done during Winter dormancy. Also iany container plant should be fertilized during active growth. Once a month with a complete, liquid fertilizer would be fine, though there are a variety of protocols, products, and schedules for applying fertilizer.
Don't water on a strict schedule. Always judge if the plant and soil are in need of irrigation. Normally one wouldn't water a dormant fig much at all, but if it is kept indoors in a warm house, it might need a little.