I was sitting up in bed sat week and it fly like I pulled a muscle, however, it s a very specific localized area. If I had to guess, it feels like a small tear. It s a small quarter sized area just left of my belly button maybe 3 to 4 inches away and level with it. It has progressively gotten worse over the weekend. Now it hurts when I lay on it, cough , or exert my stomach muscles in any way.