hi enara! sounds like your rubber tree
is suffering from a couple of things. one of which is the light change (it is nearly impossible to match the original grower's conditions in our home) it is not uncommon for plants
to loose leaves when the light change is drastic. one way you can help this is by replacing any incandesant bulbs with the compact florescents.
another thing that is probably happening is that the watering is off. either too much or (less likely) not enough. your plant
should be dry to your first knuckle when you stick it in the soil before you water it, then water thoroughly.
also, check out the garden helper's pages on rubber tree care