M.R.
I don't have any advice for stopping suddenly but wanted to share that going back to work is not always a reason to stop--I worked full time and breastfed both of my children (my maternity leaves were 6 weeks). Find out what your state's laws are for employers--NY employers have to accomodate a nursing/pumping employee until the child is 3 years old if the parent wants. You know what is best for your family, but working and pumping is doable! Breastfeeding for the first year is so good for your baby (and for you) that it would be too bad if you feel you have to stop for work.
If it is too difficult, you could substitute formula when you are at work and nurse when you are home just to make that transition easier on both of you. My hormones went nuts when I weaned.