I know how you feel about being away from your family while you are at school. It is so tempting to go back to them because it is safe and secure and it is what we know. Humans are terible for hating the unknown and many shy away from it. You could look at it as a chance for a new exciting adventure. (Just a thought). There is nothing wrong in seeing your parents, but try to mix with the others as well. There will be many (mainly freshmans... I think thats what you guys call them over there) who feel the same as you. You are not on your own.
My other thought is that there is no point in going to a school where you cant study what you want to. If you want to be a psychologist and you want to study Psychology, then there is precious little point in going to University College London and studying economics. (Just as an example... You get what I mean though) Do you know what you want to major in? If not, then I would suggest looking at what you are good at and what you enjoy and trying to find something you can make a career out of.
Please dont feel like you are on your own. We will give you as much support as we can. Let us know how you are getting on and keep posting!
I would definately go back to seeing your old doctor if he/she knows you and the issues better. It sounds like you need some support from a medical professional. Also, school councillors are limited as to what they can do, where a doctor (pretty much has) free reign, if you know what I mean.
As for the possibility of Bipolar, im not 100% sure as I am not a doctor and I dont have a great understanding of Bipolar, but my gut reaction is that it is Depression rather than BP. BP is a rollercoaster of highs (Mania) and lows (Depression). During manic phases, people are often as high as a kite (emotionally) and behave as if there are no limits to what they can do. During depressive phases people are very low and can struggle with daily life. For more information on BP, you could try the BP Forum or lok at some of the BP rescources we have (http://www.healingwell.com/community/default.aspx?f=13&m=350839).
I hope this helps