Is Fainting A Side Effect Of Depakote And Nadolol?

I was on 250mg of Depakote Er and 20mg of Nadolol for migraine prevention. Two nights ago, I woke to urinate, but fainted on my way, with no warning, smashing my face into the cabinet. My husband helped me up and I fainted again falling into our soaker tub. I was unconscious and unresponsive. My husband called 911 and after asking him a bunch of questions, they instructed him on CPR. I moaned so the dispatcher told him to discontinue. The medics were very scared by my vitals and brought me to the ER. They assumed I overdosed and did a thorough urinalysis. No drugs found and actually said my Depakote level was low. My headache specialist doubled my Depakote Er and took me off the Nadolol. My symptoms match that of an overdose of Depakote. Question: Is it possible that my body is sensitive and 250mg is actually too high for me?