Tight stomach symptoms and conditions

Hi,
Im a mother of a 19year old onYasmin. she's bloated and has a tight stomach; but worst of all, she's had blood in her stools. Her friend has had the same thing and went off right away. has anyone else experienced such a thing? we aren't sure if it is the pill but I really don't like her being on such a toxic thing. Ive suggested other non-chemical birth control options.
worried mum