V.W.
I have 3 girls; 17, 12, 7 and two boys 5 and 3 months.... Sounds to me like he has developed his fear of strangers - usually around 8 months babies can develop the knowledge of who is familiar and who is not - when they realize this they want mommy even more because they have suddenly become aware that mommy goes away...
He will out grow it - I know it's hard, but enjoy it... Next thing you know he will be a senior in high school and you will be lucky to get ONE hug everyday - that's if you even see him....