No you're not the only one who was gaslighted. It's a common cause of trauma. I survived my mother's cult, where gaslighting was their whole schtick. My father literally survived Nazi imprisonment as a child, as well as multiple childhood near-death experiences, one of which killed a caregiver in front of him (a soldier in urban combat), another an explosion that left him maimed; he was a gaslighting, explosive rageaholic. I loved them both, I survived them both, maybe because they loved me - so I was relatively fortunate. And I developed complex trauma, depression, intrusive rumination and suicidal ideation. I regularly cried, and I regularly shouted.
Therapists were disappointing. One was so freaked out by my abuse story that he said nothing and eventually explained that he couldn't cope. The other told me how much she was impressed by my survival story and then touched me up without my consent. I fired them both. Therapy helps many people - but don't yearn for therapy as if it's the Promised Land, because it's not.
Self-help books are at least as good, if not better in my experience. Personally, I read about cults, war trauma and recovery. I looked for the 'vulnerable narcissist' inside myself and tried to dissolve him. I learned about the 'internal locus of control'. I practiced gratitude and tried to practice kindness. I cut alcohol and increased exercise in nature. I changed job, worked on my friendships and quit those that weren't working.
Today, I am very well. My trauma didn't make me special, my recovery made me blessed. If I can do it, anyone can. Very best wishes to you and your recovery.