Do you have other chicks or just the one? The comb looks very small, more like a hen. Generally I sex my chicks by comparing them to each other; it's harder to tell with just the one. At four months you should be able to tell if it's a cockerel or not. Are the tail feathers long and pointy, or shorter and more rounded?
Hello again. ) I actually looked at this bird for you on the New Members section. This a very unusual bird. As I said on the NM post, it's likely a Light Brahma mixed breed pullet. It's a very pretty bird.