Why does my stomach hurt during period?

During a period, hormonal changes are taking place in the

body. This can cause discomfort for some, and nothing for others. It is common to have stomach cramps, feel bloated, and have pain in the thighs and back. Some girls also have headaches, constipation, nausea, dizziness, and in extreme cases may faint. It is also normal to have less energy, tender breasts, and acne.