First of all, let me applaud you for returning to work, it is hard having to part with your new baby, so soon after birth but knowing your child is in the capable hands of your mother, will ease that for you a little bit.
I would agree with the other person who said that you should consider starting back on a friday, that way your can get your bearings after maternity leave.I would say to call home during lunch or plan for a few "visits" during lunchtime from your mom/baby to ease your transition back into work.
Having a job right now is a precious thing, especially because of the way the economy is. You should maybe look at this too as a chance to have a little bit of yourself back. You said you love your job, so this is a good thing too. I think it's pretty mean that moms are shunned for wanting to work outside the home, thinking it will somehow stunt their child's growth. My parents and several of my friends parents all worked outside the home and we are all respectable human-beings. Having a dual income family is a normal thing too...Don't feel bad for working, your child will one day respect you for doing this on their behalf!