I'm nearly 15 and can't ejaculate. I can feel pleasure when I masturbate but nothing comes out

I'm 14 going 15 in a few months and I think I have a problem. This has been on my mind almost everyday for the past few years and I'm starting to feel worried and self conscious about it but basically I can't ejaculate. I masturbate and eventually it feels great but nothing comes out. Can someone please tell me why this might be and at least stop making me feel bad about myself!! Thanks