Its very normal... it only lasts until they get in their teens though. Then they are defiant with everyone to see how much they can get away with... even worse with that person they are closer to. Its up to you to stand strong and demand that he not be so clingy if that is what you want. If everytime he cries you run to the rescue and 'baby' him, that is what he will expect. Where as, in a daycare center, most of the time they can't be as nurturing due to the amt of kids they have there... they brush them off and send them back to play.
I'm by no means suggesting that you ignore all of his crying or wanting to be with you, but I would start slow with 15 mins at a time where he sits with his toys and you go and do something else, out of his site but you keep him in yours. Slowly work your way up week by week. He needs to learn how to entertain his self, creativity is really important in his early stages.