All I`ve Ever Wanted To Do Is Act

Hello.all i`ve ever wanted to do is act, but im 16 so i feel like i would be starting too late.( i plan to start after i graduate from a university to study acting) seriously, it`s all i`ve ever wanted to do, but my biggest issue is lack of confidence. I honestly think that i have potential and that i could do it, but my insecurities cause me to hold back a lot and that totally blows it. Ive always wanted to be like Drew Barrymore or Julia Roberts,ect.(there`s too many amazingly talented ones to name) but i don`t know, something inside makes me hold back and i can`t do that, because i know that that`s biggest thing keeping me from becomming everything i`ve ever wanted to be, which is really heart-breaking. So if anyone has any suggestions or advice, i would really appreciate it. Thank-you so much.