Yes, you have a short.
Use the search function of this forum and you will find others who have posted similar problems and have gotten responses to explain the problem and how to resolve it. You should also visit your local library for a good MRR book on layout construction and wiring. For the most part, wiring is wiring. The basics apply whether you're using DC or DCC. A short is a short.
Here's a tip - draw yourself a diagram of your track plan. Use red for one rail of the loop and black for the other rail. Any place the two colors connect you'll have a short.
One critical bit of information you didn't provide is, how many sets of feeder wires do you have connected to your layout. It sounds like you have something wired wrong.
I have only one set of feeders on the current layout.
I did find what the problem was! no faulty wiring, but faulty crossover. I followed your advices and looked at each rail separately, everything was fine, so the only place where "current" could cross was at the frogs on the faulty crossover. All this is probably old news to you guys, but not to me: the frogs are metal (they can be powered for short base locomotives), and there is supposed to be a very little gap between the frog and the rails which technically insulates the rails from the 2 different polarities where they meet...well, one of the rails was touching the frog effectively connecting two rails of different polarities when the train comes and fills the gap on the other side of the frog....
anyways, it was an easy fix, just reinstated a small gap! thanks...