Well i cant poop so please help me?

I havent been able to poop for days! I have even taken xlax and nope nothing! I have been farting alot though but they dont smell so normal they smell like very very sour milk that has been lefted out in the sun for weeks mixed with rotten eggs. I would think that since i have been farting that it would push down the poop in my body but im not sure whats happening! What should i do? sit on the toilet some more? Reach up my hole to see if i even have any poop waiting to be pushed out or go to a doctor?? HELP