I slouch and have big tes!,,, ?

I slouch, I'm 21 and I don't want to look like a hump back whale when I'm old... I know that the solution would be is to sit up straight! but do you know any way to trick yourself or steps to it. I also am very shy about my I'm really small and have 36C so when I sit up they stick out and I feel like i tryin to show something off when I am not!