If his pain is a 20 out of 10, please take him to the ER immediately! Even if you do not have insurance, they must evaluate him and stabilize him, regardless of your ability to pay. If you are worried about a hospital bill, many hospitals will offer "indigent care" to those uninsured, or who can't afford it (ask to apply), or will offer sliding scale fees or payment plans. He may be suffering from a very severe condition, such as intestinal ischemia (lack of blood flow to an area of the intestines that causes necrosis of the tissue, and can be fatal), intestinal blockage, ulcerative collitis, diverticulitis, or fecal impaction. At this time, laxatives and/or enemas or anything else over the counter that might provide relief may be dangerous, since you don't know if there's an obstruction or impaction present, and may make the pain worse, since he won't be able to pass fecal matter on his own. In the case of severe constipation, having him drink plenty of liquids and taking NON STIMULANT stool softeners like colace (not peri colace) would be advised. Walking around may help stimulate the bowels as well. In the pain that he's in, however, this is best and most safely dealt with in the ER.
I hope this helps!