Essentially everything you say is what happens at puberty, first length and then girth so the thickness. If possible, wear looser clothes and darker too to disguise things if you can. Kids make fun as they know it is embarrassing you. In showers, not much point in hiding it as others can tell what you are doing, others will catch up but just your are what is described as well endowed. As for swimwear, as before, can you wear dark material? It's an age thing, still classed as a boy but physically a man. You are doing absolutely nothing wrong, it's others people's problems, it's human nature for people to look, think of women with a large bust, you've got the male equivalent. Things will sort themselves out in time. Good luck.