Fear can manifest itself in different ways. If he's dragging you over to see them, he might not be fearful. However, you have to remember that he HAS been in many scuffles. Even if he has never lunged at another dog under your watch, he HAS been in fights. Therefore, it'd be completely natural and expected of him to be nervous or anxious the first few moments he sees a new dog.

It certainly sounds like your pup is being "not-truly-dominant". A truly dominant dog doesn't have to resort to mounting and humping strange dogs. What he's doing is more overly exuberant adolescent behavior, and the other dogs are telling him to back off. They are giving him warning signs, and, when he doesn't heed them, the warnings escalate into fights.

So your job is to teach him that no means no. If he's trying to hump or engage in rough play with another dog and the other dog turns away/tries to run away/growls, first let your dog walk away. If your dog doesn't walk away and he keeps pestering the other dog, correct your dog and lead him away. Engage him in something like fetch or let him play with a more tolerant dog.