Extreme Fatigue anyone?

I am 20 weeks pregnant on my 4th baby. Until I deliever my 2 girls are with there god ~mother. For the first months of my pregnancy i became very sick so I couldnt work. Now im feeling way better, but the weather is beating me. I wake up with energy and after eating I feel tired again. I have a 20 month old son to run after and feel bad im so sleepy. Tomorrow is the big day to find out the sex of the baby that's a postive thing,but im ready to not be pregnant anymore.