Doubts over my dx

I was diagnosed a week or so ago with bipolar type II, and fully feel that it is correct, but still have some lingering doubts in my mind over whether I truly have the condition. I've been told by my counselor at school and several others that this "could just be a phase" (I'm 18, in case that matters), and this makes me nervous about whether I should fully embrace my diagnosis or not. Whether it's my own personality, or some disorder, I'm a person who will go over something literally hundreds of times in order to convince myself that I'm doing the right thing, and these comments have been only exacerbating these thoughts. Any opinions on whether these comments by others have any merit?

Were you diagnosed by a doctor?
Also, read up in it. Match your symptoms the that of which you read. I have books and websites that I go to regularly to educate myself on this condition I have. Took a long time to cone terms with it, but the symptoms fit. So then it became a matter of learning how to live it so I can still enjoy life and get through tbibgs .

Yeah a psychiatrist diagnosed me. And I took a blood test for certain thyroid hormones, which came up normal on all accounts. From all I've observed, my condition fits bipolar disorder as well as it should in a real life scenario.

Best advise I can give is educate yourself on it. Find things of encouragement, find tools to deal with certain moods and really anything else you can read up on.