How to get dog to walk on loose leash?

I've been trying for 2 weeks to be a "tree" and stop moving when she pulls. This isn't working - does it take longer? I also try turning around and walking the other way - no results either. She isn't pulling my arm off or anything but she is keeping tension on the leash enough to pull somewhat. Are there any other methods? I use a regular collar and 6 foot leash. I am having a baby in November and want to be able to walk her with the baby stroller. I know of the head halter and will try that as my last resort, and I will not use a prong collar. I don't know if breed matters but she is a pit bull. and no I don't want to hear of any pit bull horror stories, I don't buy into them, sorry.