It sounds like you may be constipated enough that stool is blocking your intestinal tract. You can use over-the-counter stool softeners and laxatives. At this point you will need to work on this for a few days most likely.
Drink more water than you are accustomed to, so there is plenty for the bowels to use to move things along.
Take a stool softener twice a day (ask the pharmacist at your local drug store which one to use, common names are ***** ***** DSS), and a laxative. Milk of magnesia works well; so does Dulcolax tabs (use once a day). If this does not work by tomorrow, you may need suppositories or enemas. You can also get these at your local drug store.
Also, you should eat mostly fruits and vegetables until you get relief. Meat, cheeses and carbohydrate type foods may aggravate the problem. The exception would be whole grains that have plenty of fiber, in the form of cereals rather than bread.
Once you get cleared out, you can help stay regular by eating plenty of fiber foods and/or take a daily soluble fiber supplement (examples would be Metamucil, Benefiber).
If the stool softeners and laxative does not work, you have more pain, you are not able to have a bowel movement, or develop diarrhea) this would indicate that you may actually have a bowel impaction. You will need to seek medical care in this case.