I am passing blood with my stool since today morning. There is burning sensation as well. Is is serious?

It's hemorrhage, it's probably because you drink too little water. If it happens just every time you excrete, you need to hydrate yourself more. But if it bleeds even before or after, it must be something more serious.

http://www.mayoclinic.com/

Anyway, Yahoo Answers is not really the best place to diagnose problems, so i suggest checking with a doctor.

u need to do the Endoscopy check up. a tiny little tube run from your mouth all the way to your stumoch with a tiny camera at the end to see what is wrong inside your stumoch. Doc will put you to sleep so you feel nothing till you wake. is safe & easy does it.

yep.

Go to a Doctor asap

my mom had same problem, turned out she had a bleeding ulcer