sports injuries

i do a lot of different sports: basketball, volleyball, swimming, soccer and track &field. i’m having problems with my left foot, I keep getting minor ankle and knee sprains and some bad cramps. always when i’m injured, I wear ankle or knee support/brace. how can I prevent injuries? should I go see a specialist? but i’m still a teeanger and my parents don’t allow me to visit a specialist because they think my injuies are not at all an issue. can someone please give me some advice? thanks