How do i handle the discouragements at the gym?im 16!?

im 16 and a half and kinda look like a kid {though im not} and everybody is like starring at me and askin my age and keep on telling me-"ur too small,do only light weights,your height will stop,u'll remain short" ..i mean is it all true???is this not the right age!! then when should i start gyming{weight liffting cause i want to look bulky n hunk} please specify age -when to start...right now im consuming UNIVERSAL'S -GET BIG 3100...my weight is 50 and my height is 5 8".plz plz plz...help!! expert aadvice even better n experienced ppl most welcomed!!