To walk or not to walk: Third trimester back pain

[wonko]

I'm currently 30w1d and a 34 yo frm.  I'm also on the heavy side (obese by BMI standards).  The primary exercise I've been doing during my pregnancy is walking.  Prior, I was doing elliptical for cardio and also weights at the gym.  However, due to my risk factors my docs told me to do more gentle exercise and to not let my heart rate get over 140 bpm.  Thus I switched to the walking.

In the past week, I've developed some strong lower back pain.  At first I tried to ignore it and continued to walk.  But by the end of the workday on Friday the pain was very bad, and I spent all weekend resting and icing my back.  Standing and walking both seem to exacerbate the pain.

So, my question is:  Should I walk through the pain for the benefit of exercise, or should I stop walking?  If I'm to stop, any ideas for gentle exercise for 30+ weeks?  I tried a beginner's prenatal yoga DVD but I was terrible at it and honestly couldn't get into the whole meditation side of it, anyway.  Thanks in advance!

[FreJo]

How about swimming? I love doing it especially in the third trimester of my pregnancy.
It's good but gentle exercise plus you feel so light while in the water.

[Glad2beMom12x]

I wouldn't continue anything that causes pain. Seeing a good chiropractor could help. It sure helped me go from severe pain to feeling great within 2 adjustments.