I've lost 15pds in 12days. hsve rectal bleeding in stool an tissue. cramps sharp pain in stomach. cant go with out fiber pills lax. bloating vomiting?

NO: No you should see your doctor first , for full physical examination, blood tests, endoscopic examination along with radiological tests to find the cause of your symptoms. Some one at your age a malignancy is unlikely, may be ulcerative colitis, or other conditions that could be cured and get it treated with out delay.

See a doctor: Sounds like it is time to see a doctor to find out what may be wrong. Cannot tell in this forum what may be the problem without more history & information. May need to have some tests performed.