Come on, Dad. THINK about what you've said here for a second, and perhaps you'll start to see the light about a few things. Your boy may be 16 now, but he was only TWELVE when his mom died. And it's obvious to me that he's never gotten over the loss. All these behaviors you've seen lately are signs that he's still grieving, and grieving INTENSELY. He MISSES his mom, and he's undoubtedly TERRIFIED that he's going to LOSE YOU, too. And underneath the fear, pal, is a lot of ANGER. It sounds like your son is going through a time when he's basically mad at everyone and everything, including BOTH YOU AND his mom, although he can't admit this openly. He may be mad at you because his mom died, and believe that you were or are somehow to blame for what happened. It makes little difference in his mind that his mom's death most likely had nothing to do with you- it could have been from cancer or a heart attack, or something of that nature- but because it happened on your watch, and you weren't able to prevent it, your son is most likely blaming you for it anyway, regardless. That's just human nature, sir. People who are grieving a loss like this will inevitably look for someone or something to blame for it, because that makes them feel less helpless and vulnerable. He's almost certainly mad at his mom for DYING and leaving him alone with only you as a companion.
No matter how old a person is, or how much they grow up, or how mature they think they are, they will NOT take rejection well. It makes no difference whether a person is 6, 16, or 60- rejection is STILL REJECTION- and death is the ULTIMATE in rejection because it's the ULTIMATE abandonment. Rejection HURTS, pal. It hurts a LOT, and the pain from this kind of rejection- caused by death- can last for years, even for a lifetime. And your son is experiencing that rejection first hand, and has been ever since his mom took her last breath. YOU undoubtedly have experienced this too- but in your case, you appear to have recovered a little more quickly than your son has. Or it may be that you're simply a little more resilient than he was and is. There's NO timetable for grief.
The first thing you need to do is get your son to the doctor for a full medical evaluation, just to be sure he isn't experiencing physical problems that could be making the grief he's feeling worse, and/or interfering with the healing process. While you're at the doctor's office, you need to be very candid with him or her about what is going on at home and what your son has been doing. Tell him or her about the bedwetting, and the fact that he's so unnaturally clingy and keeps crawling into bed with you every night. Any trained physician will recognize these symptoms for what they are, which is indications of stress caused by profound grief. Ask your son's pediatrician for a referral to a psychologist or psychiatrist, preferably one who specializes in treating adolescents with bereavement and grief issues. And then make an appointment for the boy to start seeing that professional as soon as possible. YOU also need to look into getting some grief counseling for yourself, too. And it wouldn't hurt for both of you to join a support group- you for people who've lost their spouse, and your son for teens who've lost a parent. The next thing you need to do is take some concrete steps to protect your son's mattress. Enuresis ( which is the medical name for bedwetting) has a variety of causes, and it's associated with several different medical conditions, including but not limited to diabetes and sleep apnea. You can buy waterproof, form fitting mattress protectors at most major retailers which sell bedding, like Walmart and Target. These mattress protectors are NOT the same as the old fashioned "rubber sheets" that you probably heard of while growing up. These new, modern protectors are form fitting, and they look like ordinary mattress covers. Some of the more deluxe versions of them are also thermo or heat retentive, which means that they retain body heat even when they are wet. That's an important consideration for comfort, especially at this time of year when it's so cold outside in most areas. They don't rattle the way a rubber sheet would, either. That means your son will be able to have friends over for slumber parties without anybody being any the wiser about his situation in the future. Out of sight is out of mind, especially when it comes to teenagers.
You also need to start the weaning process, and start teaching your son to tolerate sleeping alone. The best way for you to do this is to put a cot in his room initially, and sleep there for a while until he accepts the idea of sleeping in his own bed. Then you can move the cot out of his room and sleep in a different room, but one that is closer to his room than it is to your own. During this time, the rule will be that your son is NOT ALLOWED to sleep with you, nor is he allowed to wake you up unless it's an emergency. After your son accepts the idea that you're in the next room or across the hall, then it will be time to start sleeping in your own room again. And you need to learn to sleep with your door closed, and teach your son not to enter the room without knocking first. I'm sure that you probably had this rule when your wife was alive, and there's no reason for you not to have such a rule now. Your son is going to be a man in a few more years, and it's past time that he learned something about respecting the privacy of other people.
Above all, whatever you do, DON'T punish your son for grieving, the way Star said. That will NOT SOLVE this problem, and it may very well cause your son to start hating you. It will also make his behavior even worse than it already is right now.