When you say "fitted by the bike shop" do you mean that they took a look at you standing over the bike and said "that looks right" and maybe adjusted the saddle height, or did they measure your arms and legs then watch you ride the bike on a trainer for a while as they made minor adjustments finally culminating with swapping in a new stem? The former is typical of point-of-sale fitting. The latter is usually a pricy service. The former assures that the bike is the right size for you. The latter assures that everything is correctly adjusted.

I'm guessing you got the point-of-sale approximate fit, which is OK, but it means that you'll need to make minor adjustments for yourself until you get comfortable.

Numb hands and numb butt (assuming that "butt" here is actually a euphemism for something else that went numb) can both be symptoms that you're leaning forward too much. Other things can cause the non-hand numbness, but let's start with this. When in your riding position, you should be able to take your hands off the bar and hold your body in position without feeling like you're going to fall forward. This will vary somewhat based on your core strength, but if the falling feeling is pronounced this is a problem. Often this particular problem is fixed by sliding your saddle back. This may seem counter intuitive, but the idea is that to bend over without falling, you need your butt back to balance your weight. Try it standing against a wall and then again a step out, and you should get the idea.

Once your seat is back far enough that you aren't falling over, you may find that the reach to the handlebars is longer than you would like. You fix that by getting a shorter stem. You may also want a stem that angles up to effectively raise your bars for more comfort. Stem length is a tricky problem because as you raise your stem height, you also need to shorten your effective stem length or the reach problem gets worse. Fortunately, it's not an exact science and there's probably a range of placements that will be comfortable for you.

I could say more about fit, but it gets complicated and subjective very quickly. My advice would be to try sliding your saddle back and report back as to whether or not that helps then ask more questions as you narrow in on the problem.

If you feel like some extra reading, start here:

http://www.sheldonbrown.com/frame-sizing.html

or here:

http://www.peterwhitecycles.com/fitting.htm