I am 17 years old and I can safely that I know how u feel, when I was your age I developed certain actions to help with my speech like finger movements or normal hand motions and my biggest saving grace was the frequent use of uhh (or ő in Hungarian). U can also ask your parents to take u to speech therapy which didn´t work for me but I really hope that it will help u out :). And my last tip is a bit of an odd one, for me it helps when I get into uncomfortable situations because I basically build up my uncomfy/nervous meter.