How to increase my genitals size?

Hi guest,

2.5" is that flaccid or erect?

Your penis can grow into your early 20's.  We don't all develop at the same rates/times.  Some guys get big early and others later on.

There is nothing, short of surgery, that can make your penis bigger once it stops growing.  Surgery is only good for about an inch as they sever the muscles/tendons that attach your penis to your abdomen so it hangs lower.  It will also be more floppy.

Hang in there.