Comfortably riding a bike is all about the three points of contact between you and the bicycle. These points are the feet (pedals), the hands (handlebars) and the butt (saddle). If you rely too much on any one point of contact, that point will develop problems such as soreness or numbness.

You should be able to balance yourself for 2 or 3 seconds, coasting while lightly taking your hands off of the handle bars. If you have a trainer for your bike, put the bike on the trainer and try it. If you can't balance yourself even for a few quick seconds, then you're using too much hand pressure to maintain balance, instead of using more of your butt and your legs.

By moving the seat back, you will be forced to use your butt and legs more, and your hands less. After you move the seat back, you move the handle bar backwards until your hands meet the bar properly.

If you move the seat back to the proper spot, and the handlebars can't be brought back far enough, then you need a new part from your LBS to bring the handlebar back to the proper distance, or the bike is just plain to large for your body. The part required could be a new stem or and new handlebar.

Also remember that handlebar height can effect the distance between you and the handlebar.