There is actually two kinds of Bi-polar..Bipolar II is where you really really MANIC... where the manic is you don't sleep, don't slow down, do stupid spontaneous stuff- (like buying cars and boats on the spur of the moment) and there may be depression but not too bad.
The other is..... where your up is just pretty normal, hypomania.... you aren't nutty up there just okay happy.... and the depression can be really bad or just moderately bad. This is one that is harder to diagnose because it is really just alot like major depression but you don't stay down quite as long and don't get quite as happy as with a manic episode....
I was diagnosed with Bi-polar when I was diagnosed with Bulimia... The psychiatrist put me on Lithium, another medicine called Luvox and then two other medicine for Anxiety....I stayed on these for about a year and decided that I really didn't feel or think I was bi-polar that I had suffered from depression for a long time but personally just because I had depression I didn't think I met the criteria for what all he had diagnosed me with... I weaned myself off of the medications because I hated taking them and have only had one or two episodes of depression in the last 4 or 5 years...
Here is a pretty ok web site with the diagnostic criteria for the different disorders... mood disorders are very common just take it one day at a time and when all else fails get a second opinion.
http://www.psychologynet.org/
Hugs to ya,
Amy