That's great news! I love going to the gym, once I'm there. You get a buzz from working out, and it can get addictive, but for many it's jsut what keeps you going and keeping yourself healthy. Loosing weight is good if you need to, but even if you don't to start with it'll be because your muscles are developing more and your body is just adjusting. It's also improving your health in terms of heart and lung function.

Keep it up and you'll soon feel the benefits, even if you're a little achy the next day.