The 1st Sustaiment Brigade has recently changed its patch to the Big Red 1. Does my combat patch changed as well? Where would I find out?

Your combat patch remains the one you supported during the war!

Your right shoulder patch or combat patch (SSIFWS shoulder sleeve Insignia former wartime service) represents your personal history of service in a combat/ hostile fire pay zone. Thus it basically reflects what you wore on your left shoulder at the time when you were in the combat zone. Don't make it complicated! Over the years many units will get realigned, have different designations or even become disbanded. If your former unit got disbanded, would you take off the patch? I didn't think so!
Wear it with pride and be glad you came back alive.

Given 1st Sustainment Brigade is in direct lineage to the 1st Infantry Division's Division Support Command (DISCOM), the shift back to the Big Red One patch makes sense. However, as has already been noted, whatever unit you were with for combat is the SSI/patch you wear.