1) Any changes in schedule/life for him around the time this started? Any chance there has been any trauma? How long has this been going on? Any other behaviors that have changed besides this and the clinginess? Any other regression is skills?

2) Have him checked out by his pediatrician to make sure there are no medical issues that could be interfering with his abilities. UTI etc can cause problems.

3) How long had he been dry at night? Is this only happening during nap time or at night too?

4) If there are no medical issues the bell and pad is the best way to treat this. Medication usually stops working when you stop the meds. Continue to have him trying to go to the bathroom before bed. Have him only sleep in his own bed, and put a plastic sheet on the bed if you don't have one yet.

Here is a webmd article about bedwetting:

Bed-Wetting-Treatment Overview