Nether Portal does not work

As I built a Portal and tried crossing it after its activation I started hearing the sounds of the Nether but could not see anything except for the wobbly teleportation sequence for a couple of minutes. I then tried walking forward and backward and jumped. First nothing happened and then I suddenly was sent flying into the lava a few hundred feet beneath me. I tried setting up the portal in different locations but the result was always the same. This is especially frustrating since I am knew to this game and this was my first try to reach the Nether.