Trying to excercise

Kaylee • Married Oct 2002. Birth doula. Expecting #4.
As much as I can this pregnancy I'm trying to at least keep moving. I haven't even lost any of the weight from my previous pregnancy yet so it's more Important than ever that I'm not gain a bunch of weight. 
​But man my best friend kicked my ASS this morning. We went for a walk which doesn't sound like much but holy crap I was tired by the time we were done. 
​Anybody else got any good pregnant fitness tips?