My advice would be visit a few different LBS in your area, and test ride bikes in your price range. They will figure out what size of bike will work for you once you decide what price range and type you want. Once you narrow it down to a couple bikes you like, see if you can rent one at a time for a couple days, and ride your normal route. Most LBS will do this, I would look at Fuji, Trek, Specialized, Giant.

Just don't buy one from a box store unless you are very good at wrenching on bikes.