Looks like it could be this plant
Joseph's Coat (Opuntia monacanthos 'Variegata')
or the non-variegated version, I can't tell from the photo. I am kind of shocked and amazed (in a good way) the plant has survived for so long given the low light you have described. This plant is a little weird growing for a prickly pear, and the low light probably causes the stems to stretch more than they otherwise would.
My usual advice for this kind of cactus would be to provide as much light as possible, but I guess without being able to provide hours of daily sunlight, just keep doing what you have done thus far, because it seems to be working.
You should notice a dramatic reawakening with the new pot, at least in terms of how fast new growth is generated.
