About a month ago I had a busted water line under a concrete slab. I called the local leak detectors and they located the leak. Then I had someone come cut the slab open and repair the leak. Thye pressure was good for a couple of weaks and now over the last two weeks the water pressure is decreased to a good gush for a few seconds then down to a very little trickle. What can this problem be? And what should I do to fix?

Is this at every fixture, low volume?