Don't worry about it! Being your dogs "alpha" should be the farthest from your mind. Just be a parent, if you will. Yes, you need to enforce rules and train your dog, but there's no reason to dominate a dog.
I am not my dogs "pack leader" nor his "alpha". He doesn't obey commands because he HAS to... he does because he WANTS to and he ENJOYS pleasing me (well, he also loves food). He's my best friend, my every day companion, and my heart.
And with positive reinforcement, he has learned over 50 tricks at 2 years old and is constantly learning new ones and practicing old. He comes to me happily when I call his name (ok, most of the time!
), he has for the most part gotten over his fear of strangers that we worked through, he has graduated his first agility class, and is well on his way to becoming a canine good citizen. He's friendly with all other dogs he meets, he's able to walk into a store or go anywhere really and be on his best behavior. And this, plus
much more, was accomplished without physical corrections, without dominating him or rolling him on his back, or forcing him to walk behind me (though I don't allow to pull, typically speaking), or using a prong collar/choke chain/shock collar.
Most of all, we have FUN together. We have a freakin' blast and he and I both enjoy training equally. We're a team... I'm not "above" him. We have a mutual respect for one another that's created a strong bond that will last a lifetime.
I think you should be more concerned with building that trust and bond and both having respect for each other than worrying about being his alpha.