Several months affords plenty of time to witness the benefit of a medication like Zoloft. It is not unusual for a higher dose to be necessary to alleviate compulsive behaviors, if indeed the medication is useful at all. There are other medications in the same family (selective serotonin reuptake inhibitors) that can be tried, but since your son is already on Zoloft a logical next step would be to try a higher dose. Also, if your son does not experience any cardiac-related side effects from the Clonidine, one or two small doses during the day can also be useful. On the behavior front, consult Lynn Clark's book titled SOS: Help for Parents. While written for use with school-age children, the management strategy he describes would be useful for your son.