bleeding nipple and hardening baby stool from fm

My baby is 5 days old. For the first 3 days, my colostrum supply was sufficient for her. However, since yesterday, her appetite seems to grow very much. My nipples were sore and bleeding until she rejects my nipple. Should i still continue to pump? But it hurts. After drinking formula milk for 3 meals, her stools became harder and she seems to have problem pooping. Any solution?