i am 19 goin on 20 and i am about 300 lbs. from the age of 11 i have gained 290 lbs. from being lazy and eatin very late at night and others as well.... erect my penis is about 4.5 inchs. and sometimes it goes awaylike really small.. and unfortunetly i have seen my older brothers penis and its at least 8in. same parents but he has been in shape his whole life from playing sports. please help