Cramps, Diarrhea, and Constipation?

[ChipsAhoy7]

I've been having some pretty bad problems in the last few days. On Saturday I was fine one minute and then the next I collapsed on the floor was having agonizing stomach cramps and started sweating really bad. I almost called an ambulance because I thought something organ or something had exploded. But I ended up just sticking through it. I feel asleep and at midnight ended up having diarrhea. Then on Sunday the only thing that passed was a small puddle of blood. And I've been having some mild but extremely uncomfortable cramping since Sunday. I haven't had a bowel movement since the diarrhea on Saturday (save for the blood on Sunday). My father has Crohns disease, my grandfather passed away of colon cancer, and some other relatives have a history of digestive problems as well. I just want to know, it is serious? Should I see a doctor? What tests should I do? I don't have a very long history. Medically i've been healthy most of my life, i've never had to go to the hospital for any medical reason. I'm eighteen years old, and female.
Any help?