Holding 18.6 mph for 5 miles is a good pace, especially if hills are involved. loosing 14 lbs is very good too. Keep it up and enjoy. Try longer and hillier rides. It is also quite a work out the hang with geared bikes. Not that they are faster, but they don't hold a steady pace and you are always tweaking your speed. Keep at it and have fun.

Ride Safe,

Joe