LTD insurer sent me to their "independent" doctor who had never treated me - now they're cutting off benefits

I've been on long-term disability for 18 months after a back injury. My own doctor, the surgeon who actually did my procedure, and my physical therapist all say i'm not able to return to my previous job. I've been doing everything right - monthly check-ins, submitting paperwork, the whole thing.

Two months ago the insurer asked me to see an "independent medical examiner." The exam took about 30 minutes. He never asked about my actual job duties, didn't review my imaging, and seemed annoyed to be there honestly. I got a letter last week saying my benefits are being terminated because this doctor concluded i can perform "sedentary work."

My actual job involved standing 6-8 hours a day and lifting. The IME guy just said i can sit at a desk so apparently im fine now. This feels wrong. I have two kids and my wife works part time. These benefits are keeping us afloat right now. Has anyone fought an IME-based termination? Do i need an attorney? I dont know where to start.