I and 14 and by your test I seem to be just starting stage 3 (3.1 was my result). I get very self-conscious about my penis size around other males in the changing room. What is the normal size for a male just starting phase 3 of puberty?
Around stage 2 of development, boys become aware of sexual feelings and, as a result, get self-conscious about exposing themselves. Add to this that few teenagers want to be seen as different from others can cause discomfort. There are always some boys who develop extra early, so even though you are right at the average development time, you notice the guys who are more developed than you are. Somehow the guys who are nowhere close to your own development are ignored.
The fact is that every guy matures at his own rate and in his own time.
Since adult penis sizes can vary greatly (the normal range is between 3 and 8 inches while erect), the size during development can vary a great deal was well. I don't know of a definitive study on adolescent penis sizes but probably between 1 and 3 inches erect by the end of stage 2 would be fairly typical.