Itchy skin, what could this be?

For around a week I've had these bumps on my back that have been itching. At first I thought they were mosquito bites, but then yesterday I scratched one and it hurt. Now it seems like random tiny dots are appearing at my sides. I'm not quite sure what this could be. I don't think it's an allergic reaction because I haven't eaten anything or done anything out of the ordinary.