Keep riding and having fun. I started riding in September of 2004 and remember when my goal for the ride was to make it 5 miles without stopping. I now do 10 miles for my warm-up and 20 miles of hard riding as my workout. I do this 5 times per week.
It sounds like you may need some tweaking done to your bike setup. I would take it back to shop where you bought it or find a reputable shop that will take the time to make sure everything fits as it should. As you gain more experience and knowledge you will be able to do most of the tweaking yourself.