Calamondin Orange Tree
I moved my tree indoors several weeks ago due to cold temperatures. But since I did that the leaves have been steadily falling off, and recently the fruit has started falling off as well before they ripen.
You most likely have a branch growing from the root stock.
The Calamondin is grafted onto the hardy root stock of a citrus, which may be a sour orange variety.
Suckers that grow from the root stock should be pruned away as soon as they appear.