It's normal development. Don't override your DS's instincts (unless you really need the loo or something) and he'll grow out of them soon enough. He won't still be clinging to your skirts at 7 if you let him let go on his own accord.

My DS was as clingy as clingy could be, now he's not. Well, sometimes he just wants Mummy, but that's happening less and less these days. I miss it! My DH is tougher too - wasn't it so much easier in the days men didn't get involved at all before children were 2-3 years old and you'd have girlfriends and nice grandmothers helping? That's when they need more rules and more Daddy sort of love!