Does Pumping Make U Tired???

I started pumping at the beginning of this week. I have been getting in 6 sessions a day. And I havent event started taking the herbs (no meds). My boobs are sore... And I think a little bigger. But everytime I pump, I get sooooo tired. At one point I went home from work (my office is 3-5 min away... so I sneak away to pump) and ended up falling asleep for over an hour! Is this normal. I am not making any milk yet. So I dont see why the pumping would wipe me out. Any feedback would be helpful Thanks