commonly used in Houghton-Le-Spring, England. Means that you are angry, furious. People in that area (Sunderland, England) say it without pronouncing the 'g'.
Sam spent all day thinking he was repairing his car but really he made it worse, we asked if he was "Fuxing " it or fixing it.....we all knew him too well and everything he tries to fix he really fuxing it