Night shots

Unfortunately, the problem is severalfold.  Although our eyes are able to adjust to light levels over an extremely wide range, camera sensors can not.  The sensor can have its sensitivity adjusted by changing the ISO setting, but doing so does nothing to change the span between the darkest and lightest levels at a given time.  Increasing the ISO sensitivity also increases noise in the image.
The second aspect of the problem is that the lens you are using, does not capture as much light as a more professional lenses that you might see at a pro or major college night game.  
The last part is that no camera can really meter well in a situation where there are very, very bright lights and what you want is something that is being illuminated by those lights.  Think of it like you wanting to take a picture in the daytime with the Sun in the picture.  It isn't going to happen.
So, what to do.  Fortunately, you own a very good camera that has the ability to use a much better metering system than is currently available for purchase - you.  Put the camera on Manual - the M setting.  
Next set the shutter speed according to this rule - 1/the focal length you are using, or faster.  That means that if you are using the lens at its longest, 70mm, set it to 1/70 or faster.  Next, since this lens is not that fast, set it to its faster f-stop - which is the lowest number.  Now, take a picture.  It will probably be too light or too dark.  Use the ISO setting to adjust the sensitivity of the sensor and adjust how things look - a higher setting if things are too dark, lower if they are too light.  Take a few more pictures and you are done.  Here is the one positive to go along with the negatives about photographing night sports - the lighting never changes.  
Something else to know, apart from the using the ISO to adjust the exposure, this approach will work for you all the time.  If you are in daylight, set the ISO to 200 and leave it there unless you can't get a good shot following the shutter speed rule.  Only increase the ISO if you can't get the picture light enough while using a shutter speed fast enough to avoid blurry shots.  
One last thing.  Pros don't use the meters in their cameras for most of the shots they make in this type of situation.  Over time the trial and error process you are going to go through will teach you how to set the exposure correctly about 90% of the time.  Good luck!

Try upping the asa number for night shots to aminimum of 400 and also the built in flash is really only good for about 15 ft of quality exposure. regrettably the cure for quality shots is the sb600 or if budget allows the sb800 flash with 15 min rechargable batteries. cures a multitude of problems out to about 45 yards.