Im not sure that what you are describing is depression. I think it is more likely to just be that you are having a hard time adjusting to things that are changing around you and hence I dont really think that the Lexapro will make you feel any better. Thats just my unprofessional opinion though... your doctor will be able to tell you better. It will take 4-6 weeks for the AD's to start working fully but usually a full course of AD's (in the UK) will last 12 months. If this is depression, chances are there is a cause and you need to try and resolve that before coming off the meds... thats why the course is 12 months. (To give people a chance to complete a therapy course.)
Keep us updated!