I said, yes, but he is a cavalier and its there trait. She says its not and he is guarding me???
Oh dear -- that is typical advice from really crap trainers and please do not use that person. I also would not use the Dog Listener book -- there are some good things in it (and in the past, I interviewed the trainer for my newspaper and attended her seminars) but the stuff on guarding etc is just really outmoded -- eg eating before the dog and so forth. Plus: you have TWO different and totally separate issues here and only ONE is a problem.
On the issue that is NOT an issue -- as you rightly believed in the first place, cavaliers normally follow their owners around; this type of desire to be a constant companion and always have you in sight has been bred into this breed's background for hundreds of years! Also, just about any dog will bark when the doorbell goes -- indeed most of us actually WANT such behaviour as it is a good warning and a good deterrent (better, police say, than an alarm) -- though of course you want a people friendly dog when people actually come into the house.
How any trainer could think this totally normal behavoiour is 'guarding' or a problem is beyond me -- this is why I only recommend trainers who actually have some proper training and certification, and have proper knowledge of normal dog behaviour (too many just call themselves dog trainers because they have read a couple of books and think they are good with dogs -- a lot of them are anything but
). There isn't such a thing as 'little dog behaviour' that is any different from big dog or medium dog behaviour, either
. There are however some breed behaviours and cavaliers like to be people's shadows. How sad that a trainer would jump to a potentially damaging conclusion and suggest what could easily be a training approach that could cause real anxiety to your cavalier and cause new problems!
If you want a decent trainer, get someone with a CPDT or APDT certification (preferably the first). Their website will list trainers internationally near you.
Now: the actual problem you have is a dog that doesn't like other dogs. That IS an issue that can become more and more serious. Can you explain more about this? Dogs that do not like dogs generally are like this because they weren't adequately socialised to lots and lots of dogs as a puppy (the first year is very critical for this) and also because they are not continuing to meet enough friendly dogs each day and week. For example if a dog never really meets any other dogs but others that share the house or the same one or two that belong to friends, then they can become dog aggressive/fear aggressive towards other dogs because they lose their ability to read other dog's friendly signals and/or ignore them and lose the abillty to socialise in a normal friendly way.
One of the best ways to help a dog avoid the sad fate of not liking other dogs is to do a fun, rewards-based training class at least once and better, two or so when under a year, so the dog meets lots of different dogs and people.
And then regularly use a good doggie day care, or do at least one fun class a year, or get involved in dog activities like agility or obedience, or find a group that meets for dog group walks or playdates.
But as for where you are now: I'd look for a good CPDT- trainer run GROUP class and go along and talk to the trainer to see if your dog would benefit from that as a starting point for learning how to again mix with other dogs. If not, your dog may need solo work with you and the trainer -- there are things you can do to recondition your dog to not be aggressive/fearful of other dogs (and this is a very hard life for a dog to live; very stressful for the dog and the owner on walks, travelling etc). BUT this does take time and commitment from the owner -- there are no quick fixes and this cannot be done inside the house but requires slow work outside the house with your dog on a lead, giving positive feedback (NEVER punishment) to slowly have the dog associate good things with other dogs, not bad things as now.
You can read more about why you may have a dog with fearfulness issues here:
http://www.dogstardaily.com/training/fearfulness -- also
http://www.dogstardaily.com/training/preventing-adolescent-problems -- all this applies to meeting other dogs as well as people. Addressing issues with a fearful dog is best done with a rewards based, CPDT trainer as it is very hard to do on one's own and not risk creating further problems.