Help!

I have refrained from running due to my sciatica, I have been doing exercises to combat it and they seemed to be working really well.  Now that I have been pain free for about a month, I decided that I really must start to try running again as its my weakest disicipline.  So I went on the treadmill at work in my break, walked for 3 minutes and ran for 1 minute, I did this three times...that's all...and my sciatica was back! What can I do, how can I combat this, its driving me mad.  The doctor just says rest, but then I just get lazy which doesn't help me at all.  I feel, apart from my cycling I am back at square one.  I had reached the point where I could run for 20 mins, now I can't do more than a minute!