I agree with the others.
My daughter is 13 and I would be devastated if she punched me for any reason. She wouldn't do it.
Your mum grabbed you for a hug and you punched her? What does that tell her - she tried to be kind and show you she loves you and you hurt her.
I agree that exercise, getting off the computer and doing things - including housework to make up to your mum and show her that you really are sorry - would be a good start. I also think you need to think again about your statement that you don't need meds or therapy.
Shula