Working out while I'm pregnant

I'm 17.5 weeks pregnant. I was active pre pregnacy and then I got pregnant and the all day sickness and constant fatigue kicked in. I barely had enough to run around with my 2.5 year old son and go to work. Now that I'm starting to feel better with the sickness (thank goodness) but I still have the constant fatigue. How do fit pregnant mothers find the motivation to go to the gym? After getting up 6am then dropping off my son at daycare working 8-10 hour days then pick up from daycare I just wanna go to bed. My 1st pregnancy was nothing like this, I was constantly active and fine no sickness fatigue it was awesome then this one is like hitting a brick wall running full speed haha. Let's just say May 27th can't come soon enough for me and my husband.