exercising during 3rd trimester

Sky

As of right now I work a pretty physical job, my last day is December 20th as my back just can't do this anymore. I am just curious how to continue exercising within reason. I have gained 5 pounds (lost 20 my first trimester, gained that back plus 5) this pregnancy and am 27 weeks now. I want to gain healthy weight from here on and not become stagnant.