I've been doing pushups for 3 weeks now. I don't do them every day...I rest every other day. But for some reason ..I havent did any pushups in 3 days and My chest still hurts when I try to do any pushups. I dont even think its a muscle cause when I push aginst the middle of my chest, the bone ...I think its called the sternum....it hurts. Whats wrong?