Masturbation issue... Please help

Hi, guys. This is pretty embarrassing, but something needs to be done. As of a few years ago, I was jerking off regularly. After a "tough breakup" (everything seems important in middle school), I stopped. Completely. Recently (I'm 16), I realized it had been so long, and I decided to do it again. Unfortunately... I cannot ejaculate anymore. I don't understand it, it's really frustrating, and I have no idea what to do. Any ideas...? Has this ever happened to anyone before? Thank you guys so much.