C.G.
It's probably a result of the pumping. In spite of our best intentions baby is much better at getting the milk out than the pump. You should find that if you get back to your normal routine your milk supply will improve. Consider adding fenugreek and blessed thistle supplements along with outmeal to help it along.
Also, if you by chance are pregnant you can certainly continue to nurse. Most women will notice changes in milk supply, most notably in the second trimester. Aside from that if your son still desires to nurse it is perfectly safe for you, your son, and your pregnancy to nurse in pregnancy. The only exception would be if you were having pre-term labor (and even that is questionable) or if you were severaly malnourished.