So clarify your question. Do you want to know if I exist, or do you want to know if I exist as I perceive myself?
In the case of being, just the suggestion of my subconscious projecting the illusion of physical sensation suggests that I am. I exist, there's no doubt about that.
Now, is my life just a dream, or an imagined fantasy or scenario? That, I cannot answer. I have often wondered that myself. There are a million possible ways this could be true. I am an artificial intelligence, I am in a coma, I am asleep, I am dead.