If you both are in tears, then that tells me that you are pushing this way too hard and need to back off a bit. Make reading fun for him, not a chore.
Find a few words that he knows and put them on cards. Have him re-arrange the cards to make silly sentences.
I'm glad to see that you let him choose the book. If he picks a picture book, let him make up a story about the pictures that he sees.
Choral read- both of you read the words together.
When you are in the car, let him read the signs to you as you go by. You can make a bingo card with words on it and he can mark off the words as you find them. This can be done while you are running errands.
Rhyme time. Give him a word and have him tell you a word that rhymes with it. It can be a real word, or a nonsense word. Again, do this in the car, while you are fixing dinner, any time.
Finally, just read, read, read to him. Many people don't understand how valuable this is. Stop and ask him questions along the way- "what do you think will happen next?" and "Why do you think (the character) did that?"
I am a teacher and I try to make learning to read fun. Every child learns differently and you need to find what works best for his learning style. Experiment a little to find his style.
Good luck- I don't think you need to send him off to a center just yet... try some of these things and also try to relax. He'll get it, you'll see!