Couple things

[amIweird]

OK, so....
1. I just turned 15, and lo and behold, i have no armpit hair, my penis is about 4 inches big (idk girth), but my feet are big, my hands are really big, and the doctor said my feet will get bigger. Shouldn't my penis be bigger by now???
2. I really want to have sex, but I'm not comfortable with my size. I mean, is there anything I can do to speed up the growth?

[Bobby]

Nope. There is nothing you can do to speed up the growth except wait. Time is the only thing that will move puberty along. Your penis is fine, and will most likely grow a little bit more.

[Pika-T]

1. It will in time
2. No, there is nothing that you can do to speed up your growth, especially your penis.

[Neverender]

1. well maybe you will have a smaller then average penis, but more likely is that your penis just hasn't grown fully yet.

2. theres nothing you can do about size. NOTHING. and to all you newbies here reading this post: Nothing can enlarge your penis. masturbation dosn't work and pumps are dangerous. the girl shouldn't care what your size is anyways, she should love you for you.

[theOperaGhost]

Well...since you have no arm pit hair, you may be a late bloomer and your penis will grow eventually. But you don't really need to worry about sex, you are only 15...there is no reason to rush into sex.