Good Gloves to Prevent Ulnar Numbness
A little more information would be helpful. Are you riding a road bike or hybrid, or what? How tall are you? What is your inseam? What size is the bike?

Without this information, the best I can do is:

1) 6-7 miles isn't a long ride. If you're getting numbness in such a short distance, something is probably wrong.  

2) It could be the fit of your bike. Hands get numb when they carry too much weight. If your bike is not the right size, or if it is set up incorrectly, this may cause you to put too much weight on your hands.  

3) It could be your fitness. If your core (abdominal and/or back muscles) are weak, you could be compensating by putting too much weight on your hands.  

4) It could be a combination of #2 and #3.

What can be done to fix this? It depends on the cause. See if your bike is the right size for your body. Online fit computers can help with this. In addition, consider strengthening your core. If you ride a hybrid, consider some new grips.