Light workout?

Okay so I wasn't exactly a gym freak before I got pregnant, but I was more active than I am now. I'm now currently 30 weeks, and I feel so unhealthy and lathargic. I've mostly been doing walking this whole pregnancy but, I still feel really unhealthy. Would light workouts be so bad at 30 weeks? I mean walking on a treadmill, pacing myself on a stepper and weights for my arms.