I think my penis is to small for my age I'm 13 and have a penis length of 1.5 inches on erect and on hard 2 inches I have no armpit hair and little public hair
Don't worry it will grow. The averages aren't that accurate for a 13 year old because not all 13 year olds have started puberty. Some have also been in puberty for a couple of years and others just started.
3" is about average - again, it varies! Some guys get bigger later and others early.
Since you have little pubic hair you're likely just starting puberty. Armpit hair may not come in until 16 or so.