Lamictal Side Effects Years After Discontinuation

I was treated with Lamictal in 2014 as a result of depersonalization disorder. Shortly after treatment was begun, extreme changes in my sleep pattern appeared: I began waking at least once every night in a state where I was aware of being awake while being too drowsy to make the smallest movement, and this could last severtal hours. I also began waking repetitively from nightmares anxious and breathless, and at times I woke wondering if I was in reality or still dreaming. Said insomnia resulted in the discontinuation of the drug a year later, after which all side effects became less severe but presist to this day. Is this a common situation with Lamictal? Is this possible? I had never experienced such sleep pattern before. My then psychiatrist dismissed the very connection to the drug and implied it was all a product of my imagination.