I'm sorry I'm unable to help much, I'm too far away. You really need someone locally to see you and your dog, and more particularly how you interact together. A good one to one session is what you need, so can only talk generally, with no idea whether this applies to you or not.
I recently wrote a post for another forum about socialising, which sadly is where so many problems like yours start. I'll copy it here just on the off chance it rings any bells.
SOCIALISING:- That much misunderstood word!
What do people think of in human terms, when talking about socialising? Going out to the pub or clubbing, a wine or beer or two, dancing and chatting up the opposite sex!! So is it surprising that people, when talking of socialising a puppy think along the same lines? But really, that is not what canine socialising should be all about. Socialising is simply the wrong word for what we should be doing. Familiarising is a far better word, learning to meet and deal with all things the pup is going to come across in later life. Uncontrolled playing is not what should be happening, this is simply training your pup to be a hooligan! We want to be the centre of our dog’s life, not running off to play with every dog he sees, where the play becomes the focus and we become an afterthought.
Almost all people love to see a puppy, but few people like to see muddy paw prints on their nice clean clothes just as they are going out shopping. But they are their worst enemies, making a fuss of the puppy one day then complaining about muddy paws the next, and you go from, “That woman with the lovely Labrador puppy!” one day, to “That woman with the uncontrollable dog!” the next. Better for you to take control from the start, it’s your puppy and your responsibility. When people say to me, “Oh it’s all right, I don’t mind.” my answer is, but the next person might. Teach your pup to meet and greet with all four feet on the ground, then to sit quietly beside you while you chat about the weather or old Mrs so and so at number 46. Aim to be “The lady with that lovely calm Labrador!” That does not just happen, that comes with training. Exactly the same applies when meeting another dog. Dont stop all playing, but limit it and BE IN CHARGE! It finishes when you say. A minutes hoolie which finishes with you calling your dog too you, praising it for coming and then walking away together gives a wonderful feeling to both humans and dog. Remember what I’ve said so many times on these posts of mine, “Everything is a training opportunity!” Aim to be the place where your pup’s fun comes form, not other people and dogs.
Following on a little, I often talk about thinking about dogs in the wild. The nearest equivalent, behaviour wise, in the UK are fox cubs. I’ve often sat in my truck in the middle of the wood watching them play. But really. In this case there is no comparison between wild and domestic dogs. A wild pup will play, but really, only with it’s own littermates. Strangers would be chased off by the sire or dam. But the play period would not last long before leaving “home” and finding food becomes the priority. The pup would be forced to grow up and become an adult very quickly. Domestic dogs do not have the same priorities. Food is supplied without any work needed on the part of the dog. literally the dog does not need to even think! We do it for them. Domestic dogs have become the Peter Pan of the canine world, so don’t wait for them to become adult because in comparison with the wild canine, it aint gonna happen. Thats one reason why training is so important!
We all have different lives, do different things and want different things from our dogs. So even before we get our pup really we should be sitting down and thinking about what we want from our pup, and how best to get it. I work my dogs so they need to be familiar with livestock, sheep and cattle, birds, hare and deer. So I need to make a conscious effort to take my pup to places where she is going to meet them, so I’m able to teach her to leave them alone. Possibly if you love hiking then the same situation applies. Maybe if you live in a big city your pup might need to travel on buses and trains. As I said, think about your lifestyle and decide what your pup needs to know about. Maybe now you can see why I said that “Socialising” is the wrong word, and “Familiarising” is a so much better word. I saw a picture on here a while back, two dog walkers meeting, one says to the other, “You’re so lucky having such a well behaved dog!” and the other saying, “It’s strange, but the more I train the luckier I get.” You get out what you put in, and I don’t mean walking long distances, it’s all about quality, not quantity.