Nicklaus, are you in the United States? Our school systems have rushed to make reading skills a requirement at younger and younger ages. Kindergarten used to be for learning to be in a school environment, for playing in order to learn, and perhaps an introduction to letters and sounds.
Now it's expected that your child can read by the end of kindergarten. This is a bad choice, because many children just aren't ready yet
. This leads to them falling behind immediately, which is a great shame. It can also lead to a lack of confidence, and even the feeling that they aren't smart.
In reality it has nothing to do with that. It's just that children mature at different rates, and always have. As a teacher, it infuriates me, but that's the system.
The commenters were right: read as often as possible with him, talk about the stories and books you enjoy together, play rhyming games and sound games.
For example: I see something in this room that starts with this sound: b-b-b-b-b. Have him make a guess, and if he chooses something that doesn't start with 'b', give a couple examples. No, it starts with 'b-', like 'banana' and 'bike.' If necessary, give more hints, like its color or shape. Each time you play though, continue to use the sound as the first clue.
There are hundreds of other games to play, and they will all help.
I hope he's doing OK.