I really do sympathise with you,i went through the very same thing 16 years ago!The only thing you can do is grin and bare it,toddlers test you all the time and push you to see if they can win,i had to leave my son clawing at the carpet saying"let me die!"I can laugh at it now but at the time i felt like the worst mother in the world,try inviting other people from the nursery who he is fond of to your house then he might slowly start to see the whole experience as fun,one day when i took my son he totally changed and just waved goodbye to me without any fuss,the staff probably thought i`d drugged him!Keep it up,your`e in charge even though i know it`s one of the worse feelings a parent can have.Good luck.