Um, i've just recently been bleeding and being sore from, the rear end, im 16 and im wondering, why this would happen?

Need to examine: What you described suggests and anal fissure or external hemorrhoids. It would be prudent to see a doctor for an evaluation. You should take a stool softener to ease the passage of stool. You may take fiber laxative like Metamucil and drink enough water so that your urine is mostly colorless. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex. Get HPV vaccine

Anal bleeding: Most likely due to hard stool. Increase your water intake and try Metamucil 1 tablespoon twice a day Good luck