scared puppy

Question
i have a 8 month old dogue de bordeaux.(Vincent) He has been a wonderful puppy, loves everyone and everything, and has had minimal training issues. 3 weeks ago, all of a sudden, he became very scared of my boyfriend.  my bf has a golden puppy the same age, and they come over at least once or twice a week.  Vincent will not play with the golden if my bf is in the same room, he just goes and sits in the corner.  Yesterday I was outside, my bf showed up, went to pet Vincent, and Vincent peeed himself.  I do not want my dog to end up being a big coward since one of the reasons I got him was because I am single and live alone with my 2 kids.  Plus, I want him to get along with my bf.  do you have any suggestions?  anything will help, hopefully.
thank you.

Answer
It's very unusual for a dog to develop a fear of something for no reason at all.  Generally, SOMETHING has to have occurred to make the dog fear the object, person, sound, etc, although the reason may NOT always be clear to US.

Did you take Vincent to puppy classes when he was younger?  Did you get him out of the house a lot and socialize him well around different sounds, sights, etc?  This is one of the most important things an owner can do to assure their dog develops into a friendly, confident dog.

Vincent peeing on himself is an obvious sign of submissive peeing.  Are you able to think back to the very start of this behavior and recollect if your bf said or did ANY type of behavior that could have been frightening to Vincent?

I wouldn't necessarily categorize your dog as being a "coward" because
1.  in HIS mind, he has some reason to be fearful of the bf
2.  because of his full-grown size and demeanor, he will be intimidating to strangers even if deep down inside he isn't the bravest dog around.

How does he act around other people?  If you take him around strangers, is he fearful of them as well, such as someone passing on the sidewalk when you're out for a walk?  What if someone new wanted to pet him?  How would he act?

I'm including some information on submissive urination that I hope will be helpful:

http://www.ddfl.org/behavior/submissive-uri.pdf  
http://www.marinhumanesociety.org/Behavior/Handouts/SubmissiveUrination.pdf