Our bodies/brains hate it when they're used to getting the alcohol we've trained them to need and crave and suddenly they can't have it. They'll throw anything and the kitchen sink at you to try to distract you and unsettle you. I found a mindset of "When will this new madness end?" to be less helpful than thinking "I can take anything that comes up and still stay sober and sane, and long-term things will get infinitely better overall. This is the only way to go."
My early days (first 2 or 3 weeks) featured really bad insomnia, along with assorted other horrors like nonstop itching. I'd say the worst of the physical stuff lasted around a month or so, but the thing that worked for me to focus on was just staying sober for today. Some of those famous cliches are really true hahaha!