[BDGC]

I switched advisors in my fourth year of a neuroscience PhD. I distinctly recall wondering if it was worth burning 2+ years in a different lab for an experience that might not be better. For me, switching labs was 100% the right decision. I'm still in science, love what I do, and I'm glad I changed even if it was "too late."

Try to distance yourself a little to get perspective. Even from a one week vacation, a month in a collaborator's lab, anything to try to remove yourself and then re-evaluate. Your advisory committee can also help, once you articulate that you're considering leaving.