Lump below rib cage in centre, feels hard, does not hurt. feel when lying down on back. when i do a sit-up i dont feel it. ?

Could be a lipoma?: If it’s smooth and feels slippery it could be a common, non cancerous growth made of fat tissue. Your GP can feel this and confirm this and may have a picture taken (for example with an ultrasound) if there’s a question about what it is after feeling it. Sometimes if it’s very bothersome, it can be removed easily and rapidly.