I still haven't seen a big increase in the last six months and I'm worried. Apparently I'm in stage 4, but I've been there for a while. I have seen myself develop in a lot of areas except for the penis and testicles which still look the same as they were when I started at 13. Is it because I started at a later age? I also used to be overweight. Could that have been why they haven't developed as much as they should have? Also my characteristics haven't followed I think in the same stages as normal. I have a little facial hair, but I have hardly any arm pit hair. My muscles are undeveloped, I think, but I have full pubic hair. My issue seems to be I have never had that last increase in penis length along with a growth in penis width. I have never seen a growth in width since I started, I think, and my testicles are still smallish and don't hang, which means at times it's uncomfortable. Could I see any late changes or should I see a doctor about checking hormone levels?
Since you are developing, I very much doubt that hormone levels are the problem. Being a bit overweight around stage two is fairly typical in male development. The body stores extra fat to fuel growth in stage three.
The amount of hair in various regions of the body varies by individual. You might just not have the genes for a large amount of hair under the arms. Facial hair just starts developing in stage four and won't be done until you are well into stage five.
I would expect someone in stage four to look like they lack muscles. In stage three you shot up as your frame increased in size, but your muscles, while keeping up with your frame, haven't had time to increase in number. That is what begins to takes place in stage four and continues in stage five.
Final penis and testicle sizes also vary by individual, just like other dimensions (height, foot size, hat size, collar size, etc.) vary from person to person. The problem is that people tend judge "normality" by comparison. If you had three friends who were 6'5" to 6'8" tall, but you were 5'11"; you might conclude that you were a shrimp, but the truth is that many people in the world would think you are on the tall side. I can't comment on whether yours are in the normal range or not since I don't know your measurements.
I suspect if I, or most other people saw you, no one would think you are undeveloped for your age and stage of development. I believe your doctor would tell you that you are worrying about nothing (a common plague among teenage boys). But it might calm your fears if you just ask your doctor the next time you see him. Perhaps he'll have some time to address your concerns.
But now that you are in stage four, you can start working on your muscles. Get physically active. Go on long walks or even make things "inconvenient" for yourself, such as parking at the far side of the parking lot or using the stairs instead of the elevator, to make yourself work more. Get a job that requires physical activity. Start doing crunches and push-ups. Not only will you feel better and look better, you'll be benefiting yourself into your adulthood.