Suggestions needed!

My mum and father divorced when I was 5, my mum remarried and my step-father had 3 kids of this own. For use explaining this story I'll refer to them as "T", "O" and "L". His oldest daughter "L" is now 24 and I am 17. She lived with us for a period of time but was caught doing inappropriate things at 16 and my mum and stepfather called her out about them and long story short she tried to punch my mum because she didn't think she should be in trouble. Fast forward to today, we were at a family dinner at my step fathers family, my mum said something to me and L over heard it as my mum walked away L started running her mouth about her to O and I completely lost my cool and told her she needed to quit bad mouthing her behind her back and if she had a problem to say it to her face and we got into a heated discussion before T stepped in and told us to stop. The reason I am posting this is because when I lost my cool my tounge started tingling, my limbs went numb and my heart was racing. I was terrified because none of those things had ever happened to me when I've gotten angry, and I'm not sure what they mean. Has this ever happened to you? I don't want my mum to worry and think something is wrong with me but I'm scared there is!