As you have figured out by now, hunching or stooping are not effective at hiding your condition very well but they do make you appear sloppy. Ultimately you'll look much better if you simply stand tall. Various compression garments have improved greatly over the years and garments are now to be found that are really quite comfortable and yes, they do help conceal your condition.
Wearing unseasonable clothing, such as heavy sweatshirts and hoodies in the summer heat will actually draw attention to you. A slightly loose fitting buttoned shirt working better than many other options. Knit shirts of almost any kind tend to reveal the bodies shape a bit more than most of us would like. Be careful that the shirt is not way oversize, as that would tend to simply look sloppy.
So far as the feelings are concerned, most of us have shared the same feelings at one time or another, you can feel free to open up here as we've all been through the same torments.
You want to know what your options are. The most common option around here would be to start saving your coins and see a good cosmetic surgeon. Others find that the compression garments under a nice shirt is concealment enough. For some, they simply ignore the condition and live their lives. The only person who can say what the right answer is for you is yourself. Save yourself some grief and some cash as well, the various pills and chest exercisers are quite worthless.
You should be advised that the young ladies have their own problems and concerns. As a result, they usually have little interest in gynecomastia and while they may be sympathetic about your feelings, most don't think it is a big deal. Wisely, they seem to have much greater concern for what is going on between your ears than with what is on your chest. So you cannot use Gynecomastia as an excuse for failing to socialize with the opposite sex. I, for one, will know better.
PS I'm pretty much the old man here. Like most, My Gynecomastia appeared when I was about 12 years old. That was in 1949. Surgical methods back then were really quite crude compared to what is common now. Instead of feeling bad about your situation, rejoice that you live in a time when safe and effective surgery is available.