ditto this!The pack leader stuff has been debunked for a while now, don't worry about it.
My old dog was like that with me. Some dogs bond heavily to one person. You can help bond him to you by feeding (nobody recommends just leaving food out. for one thing, many symptoms of diseases focus on food, so if you don't know exactly what your dog is eating when, you won't notice them), walking and training him.
A vet checkup never hurts, as well. Changes in behavior can be symptoms of disease. If this worries you, take him to see the vet.