Your son is in a mixed dentition phase which a lot parents (mums especially)can find disturbing as their children are bringing out new teeth and losing their baby teeth and the teeth are looking so different or 'not so cute anymore'. It's best not to worry as it doesn't change anything. Patience is required as well as regular dental check up every 6-12 months for monitoring. Most of these issues resolve with time as all the permanent teeth come in, some children however need braces to correct the malocclusion.