You did just post. More information is needed. Lets have details. How long have you had it? where'd you get it? what's it been eating? More questions to follow.

Is the poo watery? Is the cloaca area red and inflamed? first thought is it could possibly be crypto or flagellate infection.. Fairly common in the captive reptile trade. Most reptiles are considered susceptible to Cryptosporidiosis, especially snakes. immediate treatment with a medication called "flagyl" (Metronidazole) might cure it.

We aren't vets or zoologists here. Only responsible advice we can give you is to see a vet immediately. A fecal sample and assessment of the overall health of the snake is essential for determining a course of action.