I have all the symptoms of Mania but people say that's the "normal&quo!

I did psychiatric intake work for many year and I can tell you about your symptoms:

When you are in a manic phase, this seems perfectly normal to you. You are comfortable with your racing thoughts, risk taking and thoughts of self importance. However, you should know that the rest of us do not have these symptoms.
People go through life without living with these things. Life is normal without the crazy excessive highs and the debilitating depressions.
Your family is "used to you" when you are high. However they don't know what to do for you when you are suffering from depression.
And so what is the answer here? The answer is to get medication and stay on it for life. If you are on medication for your bipolar disorder, then you need to have it adjusted because its not working to control your symptoms.
And I see you are writing from Great Britain. And so I need to tell you about one of your fellow countrymen whom we just love over here in the states, who has what you have. Hugh Laurie is enjoying a fabulous career as the star of the series "House". He is also the Executive Producer of the show and a talented director, writer, actor, comedian and musician! He has made no effort to hide the fact that he has what you have but he is regulated on his medication and totally able to function...and function well! He has won so many awards for his show and is so popular!

And so, I wish you all the best!

I'm no doctor so I can't say but I have had experience with two different people in my life who suffered from bipolar/depression. You sound like them. Not that this is what you have, it may be something else or a combination of a few things. You having a problem like this is probable and your parents are in denial if they won't even have it checked out. Heck, it's not for their health, it's for yours!

I am not qualified enough to be sure, but am interested if you were diagnosed as 'Bipolar' (Manic-Depressive)?

Life experience.

Instead of bipolar disorder, look into unipolar depression.

Even if it just has to be a regular doctor, get to one. Explain things (preferably with your parents out of the room, so they do not dismiss your feelings to the dr) to them, and they can either try to prescribe medication that may help to you, or set up a referral with a psychiatrist. At one point my psychiatrist had told me I was bipolar, but after a few more sessions, he said it may just be my personality. To get another opinion I went to another dr, and she has yet to give me an official diagnosis other than mood disorder.

mania is really really really extreme..... The last time I was manic I only slept maybe 2 hours a night for 4 months, I was meeting guys on the internet then sleeping with them in their cars, I slept with my best friends husband and ruined their marriage and my friendship, I would sometimes pull over to the side of the road and masturbate in my car..... I spent $30,000 on african violets, furniture, clothes, and about a thousand toasters (I thought I could end hunger in Africa if I took them enough toasters)... yourthoughtsracesofastyoucan'tkeeptrack ohlookatthatblouse tomorrowIneedtocleanthebasementandpaintt… herekittykitty godhescuteohI'mhorny Iwantchinesefood letsgoshoppingforfurniture butthemortgageisdueIcanpayitnextmonth Iwantanewcouch............. Unless it is having a major destructive impact on your life I wouldn't worry about it too much... if the people around you are not worried about it then it is not likely something to worry about.