If you can do so without appearing too obvious, go someplace where there are a lot of people, such as a mall where you are likely to run into people with varied body builds.
Some guys have what in the past has been called "pear shaped", something I find a bit demeaning, but that body type carries their fat in the lower abd, rear and thighs. It can happen in either men or women. There are women with no butts that wish they had one, which makes plastic surgeons happy, lots of butt implants.
Yes, there are guys who have larger rear ends naturally. Don't forget, your body is developing, and would be whether you were on T or not on T. I'll use my son as an example. When he was ten, he was lanky and thin. When he was twelve, his face was round and he was on the slightly heavy side. At sixteen, he was again longer a lanky. My son is a cis male, and these changes appear to be normal. You grow up then out then up then out.
At your age, I didn't even know there were transgenders or what they were. I wanted to fit into red tag levis, but everything that fit my waist was too small for my butt and things that fit my butt were too large in the waist. I remember feeling really down because I'd look at guys and girls who had guy bodies, you know the type, lanky with no chest, and hate the way I was developing.
After I started T, at twenty six, I went through a period where i seemed to gain a lot of water weight. My face turned really round, my jeans that had previously been loose looked like I was poured into them. part of it is genetic and part is how active we are.
Stick to good foods. Low in sugar and fat/grease and if you want to get rid of some of your rear end and thighs, start jogging. Long distance or cross country jogging will help with your proportions. Make sure you check with your Dr. and make sure you are healthy. You are young, so there probably aren't any real problems, but long runs can, on occasion, make you slightly anemic. Start with a distance that doesn't make you feel like you are going to throw up. Pick a route that you know is a certain distance, like a mile. Jog at a comfortable pace, if you have to walk a few paces every few minutes, there is nothing wrong with that, you will get the endurance. Make sure to warm up before you start. Do some light stretching and maybe some sit ups with your legs bent. They used to say that girls should bend their legs and guys shouldn't, but we learned that doing situps with straight legs causes some back problems.
No matter what you do, its going to take time. Slow weight loss is better than rapid loss because it tends to stay off better. Forget the scale. Too many things can effect your weight. Time of day, how much material is in your GI tract, things like that. Real weight loss will show up in a change in the way your clothes fit, the way your body looks and the way you feel. You can easily lose five pounds after a long run, but it will be mostly water weight. Once you are hydrated, it will come back on. It wasn't really fat.
Set aside a time of day when you jog. The same time every day. Some days you might feel lazy, but once you get going, you feel better. Be careful though. Exercise can become addictive. You may find yourself wanting to go further and further. Keep a chart and watch your progress. If you want to take your weight, take it once a week at the same time. Say, first thing in the morning.
i hope that helps some
sam1234