Your breasts will be hot, red and you will feel like crap and have a fever. That's how you know its mastitis. You can do RPS in the shower. You can nurse with the hot compress. You can express in the bathtub with a hot washcloth or in the shower too, if you know how to hand express. This works a lot like RPS to soften that part of the nipple so that baby can more easily latch on. While you are hand expressing, massage from the back of the breast down (or up if you start beneath the breast) toward the nipple, helping the milk to move out. Are you only engorged on one side? Do you have any nipple damage on that side?