Why am I shaking? Please, please help me

Exactly a month ago my now ex boyfriend cheated on me. It was incredibly traumatic. This is someone I'd been with for three years, and it's extremely hard for me to trust, love, and open up to people but I had for him. I trusted him more than anyone. I was so vulnerable and now I'm just crushed. It felt like my whole world came crashing down, and the incident even brought back my anxiety, which I haven't had since I was ten (now twenty). Suddenly I've started to shake though, which I never have before. When I think about him or what happened too much my body starts to very, very violently shake as if I'm freezing. My hands get all shaky and my body just twitches. I don't feel pain or anything it's just shaking. I don't know what's happening. I assume it's due to the stress and anxiety from it all, but has this ever happened to anyone, or might someone know exactly what it is?