My vagina burns and itches wen my period blood comes out. What is wrong with me?

Some possibilities. First, blood itself is an irritant, so you may be having irritation for that reason. Second, some women have a tendency to develop yeast vaginitis while menstruating. If so, you may need treatment with your cycles. In addition feminine hygiene products such as tampons and pads can be irritants, especially if they are scented or plastic or if you are allergic to any component in them. Talk with GYN.
Get checked. Although not uncommon to have some irritation from blood its best to get checked as infections, rashes can hide in the vagina and private area. Good luck.