I had that as a child. Bawled my eyes out when my brother started school, and when mum left me at kindergarten.
I seem to need at all times, wherever i am, SOMETHING with me, to act as like a "mother-replacement" (to make me feel "safe"). Nowadays all my house clutter seems to fill this need (& i guess i feel the "separation anxiety" whenever i change sth in house, no matter how small).
I think having separation anxiety (or "clinginess") is a result part of having major nervous/anxiety/timidity problems.
And i think i'm ever so gradually getting used to the idea that my parents will one day no longer be here. So i'm trying to rely more on
other things now for "stability" (like my semi-religious/life/god/etc beliefs). Still, when they have both gone, i feel that
half of me will also be gone, as they have been a
huge part of my life. Just will have to deal with that when it happens, but although probably 20/so years away,
already i am dreading it