It is likely to to be a COLORECTAL problem. Infection is common cause for such a problem. Colitis is the commonest amongst the known causes.
But at the same time there are many other entities which are likely to cause such symptoms
If you don't respond to a full course of antibiotics, you may have to undergo further evaluation. It may be in the form of stool examination and if required the colonoscopy.
Next Steps
complete the course of the medicines prescribed.
if unrelieved get the stool examination done for ova cyst and occult blood.
may need colonoscopy.
Health Tips
see that the food and water you take is from the hygienic source