My larrey son?

my son has reached the teens and when i tell him of or ask him to do sommat hes smirks at me and walk away laughing , i feel like slapping him , i wont cas hes bigger than me , i try talking to him and he seems to understand and says hel try harder , only he forgets it soon and then goes and does sommat not nice. am a single mum who so far has brought up four kids on her own , (father got new family now and seems less intrested) I try my best and deep down hes a good kid , just wont listen to me anymore , any advice