A common cause of stomach pain may be appendicitis which is the swelling of the appendix that leads to discomfort. It could be shown in an ultrasound, but maybe not. Visit a doctor to be examined in detail and thereby the one who will advise you on the right treatment which is mainly prescription drugs or surgery to remove the appendicitis. Look for symptoms like worsening pain, fever, or vomiting, which could indicate a more serious issue. 

Your friend might be having a serious issue like internal bleeding. The bleeding from the bottom, stomach burning, and feeling sick could mean something is wrong inside her tummy. She needs urgent medical help to figure out what's happening and get the right treatment to stop the bleeding. 

A positive result from your last two colonoscopies, showing no inflammation or IBD, is reassuring. Mucus in your stool might be due to irritation. Diarrhea can result from various causes, including infection, certain foods, or stress. Since your test results aren't alarming, try drinking lots of fluids, sticking to a soft diet, and letting your gut rest. If the diarrhea persists, consult your doctor for medical advice.

Styptovit-E is often used in various medical conditions where there is excessive or prolonged bleeding, such as heavy menstrual bleeding, nosebleeds (epistaxis), bleeding gums, and certain bleeding disorders. So please consider taking tablets only if its prescribed by your doctor to you.