You have both your age and your size on your side here which is great! What I'd suggest is, rather than looking for the most fashionable clothing items, build up a wardrobe of items you know suit you and that are fairly plain. for instance if you don't like skinny jeans and they're in fashion, get bootleg ones instead. Your fashion aspect can come from funky accessories, bags, shoes etc. look up fashion trends on the internet and they'll give you ideas of what's hot. But most of all just be yourself!