How can I be more emotional/empathetic?

You are actually very lucky. Emotions often weigh people down. Ask a depressed or heartbroken person if they like having emotions, they don't. Being relatively unemotional is great, because you can be more rational and successful in your career. At 15, you are still finding out who you are. Try to love everything you find out and don't try to be someone else or be the 'right way'. Everyone is different - that's what makes life great.