Maybe you needed a change in your dosage, or type, I know Depakote also comes in extended acting form,Depakote ER, I guess like "time release"? But anyway, as you already know, don't just stop a med. until you contact the prescribing physician. Get in contact with he or she and tell them exactly what is going on, to avoid further problems. Maybe you'll just need a change in med. one that may work better and longer for you, some meds can have a "poop out period" after several years, especially those in the SSRI group.
Larry Hoover, if he drops in, can give you more info. he is best known for his expertise in this area.

Please take care,
DE