Hi Matt:
Hey my mom was adopted too, so I know how you feel not knowing your medical history.
Your symptoms sound a lot like Crohn's, or colitis, or IBS with constipation. You probably have internal hemorrhoids too because of all the constipation, which could also account for the bleeding. The problem is, you can't diagnose this on your own. You should make an appointment to have this checked. Most likely you will just have to change your diet (add tons of fiber), but you should make sure there isn't something else going on like diverticulitis, or other infection of some kind. You are pretty young to have one, but a colonoscopy can tell you what you need to know. Try not to worry, I'm sure that is part of the problem too. Take care.