You should get whatever bike you want. You don't need another bike for your commute, but if it will keep you motivated, why not (budget permitting of course)?

Make sure that the bike fits you, and that you are comfortable riding it. If you end up getting a nicer bike, you might be motivated to ride more and longer. The weight will come off with longer rides (assuming the input is less than the output!)

I'm glad you enjoy riding. It's so much fun.