I am a 14 year old boy and I'm pretty sure my voice has finished changing. Is there anyone who takes voice lessons or is a voice teacher that has some advice?
An adult male will NOT have the same range as you! You need to find a teacher who is very well-informed about special technique to use with the young male voice. Therefore, find a private teacher who ALSO teaches middle school or high school music. They see HUNDREDS of people in your situation.
At 14, your voice in NOT completely done changing – you are still a cambiata, are a cambiata/baritone. You will have good days, and rough days – hang tough. You should KEEP SINGING, even when you feel the ground is moving under your feet – that you do not have the same notes TODAY that you had yesterday. That's the point – you want to be better *tomorrow*, right? So the snootiest professional teacher is not going to do you as much good as someone who works EVERY DAY with adolescent singers. I oughta know – I have only been doing this since 1971, the first I first started teaching vocal music. GET A GOOD TEACHER!!!!! You will be thrilled and amazed at how good you get, fast.