How to know if you're bi-polar?

Hey I’ve always thought of myself as pretty unique! And I love expressing that but I think I may be some what Bi-Polar!!

My moods are very random. I could be just sitting there calmly in a quiet room with someone or even by myself and just random start laughing my head off and go around talking about all this random rubbish and stories I made up!! It’s not like I’m possessed or don’t know what I’m doing though lol!

Then I can go from being really tired,pissed off and without energy to suddenly being hyper and annoying everyone around me!! After my hyper spell I usually slump again!

My brother and sister just think I’m a funny weirdo,my mom thinks I’m really strange and a few years ago my parents wanted to send me to a crazy house!

My friends know what I’m like and love me for it and think I’m fun and my boyfriend thinks I’m amusing and unique!:)

I don’t smoke or do drugs and have only been drunk once. I’m not allergic to anything and I’m not sensitive to anything like caffeine etc. When I’m by myself I go into dark moods sometimes and was depressed a few months ago but the doctor couldn’t tell because I can I’m not like that when I’m around others really. I have never or would ever self harm or think suicidally.

The only bi-polar people I know of are big celebrities like Britney Spears,but she had plenty of money to fund her crazy partying and meltdown and I wouldn’t ever act out like that!!

Please help!