Auk beat me to it, it is a Carmona, and the soil looks poor. It is an a very small pot too, I think you need to re pot soon, stop the fertiliser, and keep it out of draughts. It is not a hardy species so will have to be protected from frost. Don't put it in a window with a heat source under. The loss of leaves is a bit of a worry, could be due to a number of things, but I think the soil could be the main problem. You need to say how and when you are watering, you must do this properly. Allow the soil to almost dry between watering soak the soil until the water runs out the bottom of the pot. take a look at bonsai4me.com for species guides.
Geoff.