Tired and feeling large

Julie • Full time mommy to 2 amazing little boys. A 3 year old and a baby born March 16th 2016 🍀
Anyone else? As soon as I hit the third trimester I feel exhausted and huge. I'm really not "that big" my baby and belly both are measuring right on schedule and I haven't gained excess weight or anything. I just feel beat. 
How do you keep your energy up? I'm nonstop active keeping up with everything including my 3 year old and I'm just exhausted 😴
This was today at the park. I told my son that mommy was getting tired and he said "okay let's rest on the slide" lol