Have your siblings tried Lithium? The funny thing about lithium is that how you react to them is genetic. Eg, if one of your parents is bipolar and used lithium - successfully - then lithium will work for his/her bipolar kids as well.
And Lithium is a serious drug to be on, and most bipolars that I know (including myself) haven't had any success with it. Lamictal is a real lifesaver imo, if it works for you. I was pretty much chronically depressed/suicidal, with ONE break of hypomania (lasting for about 4 months), for two freagin years - then I was put on Lamictal in the beginning of September and voila - depression cured.

I'd ask to try Lamictal, in fact - Lamictal is the first choice of medication when treating bipolar type 2s. My psychiatrist failed to mention that to me before she put me on lithium and wasted six months of my time. The medication merry-go-round is a drag.

And antidepressants generally have little effect on us, and can in fact make us worse. It's not the serotonin that causes the cycles, it's the noradrenaline level. Antidepressants give a tiny boost when you take them in addition to an SSNRI, but on their own they don't do anything at all except make our mania worse.
I'm on 100mg of lamictal and 10mg of cipralex - an incredibly low dosage on both meds. I was on 200mg of lithium - did absolutely nothing for me except make me fat. 350mg of Topimax + 10mg of cipralex worked like a charm. 100mg of Lamictal works beautifully on its own, but I like taking cipralex to give it a tiny boost.

Funny how the two meds that have worked for me are both epilepsy medication. o.O