Does the mirena (levonorgestrel) IUD make you gain weight? Does it cause you to have breast pain? I had intercourse and my breast starting hurtin a few days later

Not usually. The Mirena (levonorgestrel) IUD slowly releases progesterone into the uterus. Only a small fraction of this is actually absorbed into your system. So it usually doesn't cause breast pain or weight gain. Many women on Mirena (levonorgestrel) stop having periods. However, Mirena (levonorgestrel) doesn't stop your hormones from cycling and the rise and fall of your hormones can still cause breast pain. Best wishes!