Person Possession

Looking for suggestions. My 15 mo old Flt coat retriever mix seems to be developing fear aggression. We've done tons of socialization; dog park membership, 2 rounds of obedience school, vacations, trips to dog friendly events, stores, etc. But, in the last 5 days, my previously confidant boy has literally glued himself to me. For some reason he has decided that I need protection from people he doesn't know, as well as any dog at the park that comes close to me(his dog friends excluded). Am not sure what the trigger is, but have a sneaking suspiscion that it may have something to do with a visit to the vet last week. The techs took him in back to trim nails and clipped one a little too close. He cried like he was being disemboweled. I felt terrible for him. He is super sensitive and very much a pleaser, no problems with being dominant, so am wondering if this may have caused his "Stranger Danger".

Since we both work at home, he is with us all day, but things are getting out of hand since the vet visit! He is insisting on sleeping/laying down next to me at all times. On walks with me he is becoming very shy around greeting new people. Plus we've had 2 incidences where he's decided that he doesn't like the looks of someone and started barking/growling, etc. We called the Trainer and have an appointment tomorrow. But any words of wisdom out there? Any advice. Am considering switching vets, but hate to do that as we've been with them forever and they are usually fabulous.