I have a 3 year old English Bulldog, who we have have since he was 10 weeks old.  In the past 9 mo this he has started to attach and bite my 16 year old sons crotch!  This is a random act and unpredictable.  I also have 2 daughters, age 13 and 7,  that he would never be aggressive with.  My son tries to get away but the dog is fast and aggressive.  I usually have to physically lay on the dog to get him to stop so that my son can get away.  This does not seem to be stopping and I am at the end of the line, please help with some advise or the dog will have to go.  It will break my 7 year olds heart!