How come i start cramping weeks before my period starts?

1 to 2 weeks canb be: Pms. Pms symptoms can include pelvic/ abdominal cramping, nausea, bloating, weight gain, moodiness, irritability, pain & swelling of breasts, feeling tired, insomnia, headaches, ^ acne, food cravings, ^ appetite, swelling of hands & feet, dizziness, thinking less clearly, urinary sxs & exacerbations of chronic conditions.