Peeing Blood... other symptoms?

Ok, here is the short of it.

Thursday, I went out for breakfast. I brought the left overs home and had them that afternoon and shared them with my son.

The next morning, I was feeling very sick - stomach pains coming in "waves" - coming and going - so I kind of assumed it was PMS cramps until I started vomiting. My son also threw up that morning, and I was throwing up all day with extreme stomach pain, which made me suspect food poisoning. I slept most of the day between the pain.

I woke up this morning feeling mostly better, but the stomach pain has been returning in extremely painful waves. Then I went to the bathroom and discovered I was peeing blood.

Any ideas as to the cause? Can food poisoning cause blood in the urine, or is it likely a different cause?

(Add't - I am a 21 year old otherwise healthy female)