First, congratulations on breast feeding! Pumping is definitely a chore and you're to be commended for doing it exclusively. As for pregnancy, the hormone produced by breast feeding shuts off your period. As long as you don't have a period you're safe. Pumping should work as well in that regard as regular breast feeding deos. Whenever you stop pumping or slow down considerably, that's when you should start using protection again.
there is always chances of getting pregnant when you have your periods after giving birth, you need to take a hpt for a peace of mind.