Has this been happening while you are home or gone?
Has anything changed in the home or environment of the dog?
Does the dog sleep in your bed?
If he was having accidents everywhere I would suspect a urinary track infection but since this is only occurring on your bed it appears it is a behavior issue. Dogs have a natural instinct to never urinate in their bedding.....and thus they instinctly know not to urinate on the masters bedding so the dog is attempting to tell you something or prove something by urinating on the bed and pillows.
The first step is to close off the area to the dog if you can. This will help prevent him from going on your bed, though since it is behavior associated he will simply find somewhere new to go so we need to nip this in the bud now.
We tend to think of dog urine as something nasty but to a dog it is something of great. A dog leaves it's scent in urine to tell other dogs a message. This message could be about whose territory it is, about the dog's social order or advertising mating availability. Dogs use urine to show their dominance or to claim something as belonging to them. Dogs with feelings of insecurity or who have separation anxiety may also be hard to break of this, as territory marking builds the dog's confidence. Keep in mind the above is examples of why a dog may start marking your bedding, your boy could have any number of reasons.
The good news is this can be fixed with time and Patience. Close supervision is necessary. You must be dedicated to stop the behavior of your dog and you must be consistent. A couple of weeks or often much less time of intense supervision and correction can save you a lifetime of tearing your hair out trying to find a quick fix for the problem. Some people have reported that it has only taken a day or two using the intense supervision method.
You will need to watch him closely for the next few weeks. If you can catch him in the action that is the best route. If you catch him a quick spray with a water bottle and a firm NO. If you do not catch him take him to the spot immediately and tell him NO. Then take him outside.
The key is consistency, you must keep working with him. Some dogs can train in a few days others take a few weeks. Though if you give up it will make it even harder the next time. You must deal with every spot he makes in order to get him trained.