Turn off the power immediately and get an electrician in! They should check the earth (ground) of your wiring, and also search for a short.
Any mains electric shock you can feel could be dangerous. You may even have survived so far just because you had rubber soles on your shoes...
You must have a short somewhere, connecting a live wire to the earth. The earth is often connected to the plumbing, on the assumption that this is buried in the ground. However, if the piping is not not well earthed (perhaps the mains pipe is plastic), then the short does not trip the RCD or fuse, and the plumbing all becomes live.
Another possibility is that you have electrostatic carpeting, and are getting charged up as you walk about (usually happens only with certain shoe soles). Then when you touch an earth, the charge is giving you a small (safe) shock. However, do NOT experiment with this yet, because if the other explanation is right it could kill you!