Should I exercise if I have a very strenuous job?

I got laid off from work about a year ago and i just got hired back last week. Over the year I was laid off i gained 20 lbs. I was wanting to know if it was healthy for me to exercise even though my job is very strenuous. I build aircraft tires for a tire company and it is very hard work. When I get home at night I am drained, and when i wake up in the morning my whole body is sore. So should i still exercise or is the work i do enough. My job includes a lot of pulling, and heavy lifting, and i am on my feet for about 7 hrs