Unsure of diagnosis validity

I have recently started medication for Bipolar Disorder, but at this point am not sure if this diagnosis fits me, and therefore am worried am being medicated for the wrong disorder.
I am an 18 year old female, who has lived a very stable and normal life. I was a very anxious child, stated by family members, and my memories. I remember not being able to sleep unless all conditions were perfect, and crying and worrying, and having feelings of guilt in situations that it was not needed. My mother said I was always anxious, yet a talkative, and social child. Though, unlike a lot of stories of individuals with bipolar that I have heard, I was not a problem child. Up until the age of 18 I was an excellent student. I have always had low self esteem, and was easily emotionally disturbed. At the age of 16 things started to change, I become a lot more depressed, disinterested in school, and most things. I became the different girl in a way, dressing different, liked art, etc. at 16/17 the depression and anxiety attacks started. I am remember crying and screaming, and hitting myself in my room, over issues that weren't really that big of a deal. Running away from class, feeling hopeless, and generally depressed. I went to see a psychologist, who did not give me a diagnosis of depression as I didn't quite fit the bill. I never lasted in these periods continuously for weeks, but when they came they hit me hard.
A year and a half on, I feel I'm back in the same place. I didn't go to University after I finished school because I was so disorganised, and didn't want to study (or more so did not feel that I was capable to due to my poor level of concentration, and motivation that I dearly lacked). Work got bad, and I felt like I was on going to crack, and I feel this has led me into a depression. I went from drinking 3-5 nights a week, socialising, to not wanting to go out. I am not feeling like a rollarcoaster of emotions, some days I will be completely happy, smiling, welcoming the world, and everything it has to offer. Feeling like I am working fast, and with the determination to do things, feeling happy enough to be who I feel I am, a bright outgoing girl, to feeling hopeless and depressed. This all happens in a matter of days, Happy for a day, really happy for two, depressed for two, then it feels like it builds up. But I don't show symptoms of risk taking behaviour, or being a total spend thrift or being completely out of control. I just feel like there is so much going on in my head a lot of the time I can't think, I become mean, and cry, and yell, or impatient- when depressed, and impatient when happy if things don't go my way, or to my plans.
I went to the doctor to get help (went to numerous and got the "it's your age" response), and he said bipolar, though my counsellor seems to think otherwise, saying anxiety and depression. I am worried about this, I don't feel happy, I feel obsessed in finding out what is wrong with me. I just want to be able to go to school and live a normal life, and receive the medication for the correct disorder. Currently taking small doses of pristiq 50mg and zyprexa.

I hope its ok i was curious about some things.
I am very interested in health and believe our diet effects our mental condition also.
Ive found this out from personal experience so hope you wont mind me asking you any questions so i can eliminate some things im thinking off.That would leave at least something crossed off.
I was wondering do you eat/drink alot of sugar or does sugar ever line up with or before the times you have issues.
Same goes for eating alot of carbohydrates.Do you eat much things like bread, pastery or anything with carbs a bit too often?
Also im curious do you take sugar replacements like aspartame or anything like that.It is also in soda drinks i think you guys call them in the states.Diet drinks have it also and its dangerous imo.
I think thats all i have for now.
Hopefully others will post later with more experience on the issues youve been diagnosed with.
I wish you the best and dont give up!
I suffered for many years with candida and didnt know why i was depressed and anxious.It just took me a few attempts researching symptoms to finally pin it down and i know if you keep at it you will find a solution that can help you cope.