The sounds that you listed are plosive sounds and they momentarily stop the flow of air causing stuttering blocks. This is probably not normal disfluency especially if there are accompanying struggle behaviors, frustration, and word avoidances. The best place to start support would be getting him or her to a Speech-Language Pathologist in your area. If you’re in the U.S. look online or approach the public school where he or she attends school. If he attends private school where no SLP is available you can often still receive speech therapy services at the local school. Good luck!