Yes, it does sound like your duck is coming into his hormones, and he's confused and thinks you are a good substitute for a girl friend. This is common when ducks and chickens mature and experience their mating hormones for the first time.
He's trying to dominate you. It might be a good idea to start disciplining him to show that you are dominant, not him. Since he isn't interested in learning how to behave like a proper duck by associating with other ducks, it's up to you to teach him.
Somehow, you must show him that his behavior is not the correct way to behave with a human by stopping the behavior when he does it. Restraint is usually how we discipline poultry when their hormones cause them to be confused. He'll get the idea if you are consistent and stop permitting this behavior.
Others will likely suggest getting him a girlfriend of his own species, but that will cause trouble if you don't discipline him and train him in proper behavior around humans first. Without discipline, a female duck may cause him to think of you as his rival, and his behavior could get worse unless you discipline him.