Oh huge hugs! I remember how hard this time was! 12 months on, and its seriously not even something I worry about anymore (obviously I still worry about my DS in general but the fretting I had about being at work and DS in dacyare is no longer there).
What helped me was having DS in daycare before I actually started at work, so my first day of work wasnt DS's first day of daycare also. I gradually weaned myself away from him. First day he went from 8-11, then the next time he went for longer and so on til he went for 3 full days the week before I went back to work.
I called daycare as many times as I wanted when he first went and on my first day at work. And I trusted daycare 100% which is a biggie. My daycare were awesome though and I thnk were used to crying mums!
My first day at work was spent basically a mess! lol! Work were very supportive too! So allow yourself to be upset, its only natural.
It took me about 3-4months before I actually felt like we were in the swing of things. So I think its important to give yourself time to get used to it.
DS has been in daycare since 7months, I am going on mat leave again in October for 14months this time, but we knew we were planning #2, that made the financial commitment to work easier. I am rejiggling my work hours so that when I return from mat leave in 2014 I wont be paying 2 x fulltime daycare cos that would be a killer.