I know from experience that therapy can bring up a lot of really difficult things and sometimes make you feel worse. There's nothing wrong with needing more help than a therapist can offer, but I understand that getting that help is not always an option. Do you think it might be helpful to talk to your therapist about this, or have you already? I'm not a professional, but I feel like they should be making sure you're OK when the session ends.
As far as the actual urges, I know not everyone likes to make art in some way, but I used to draw things to express my emotions when they got really bad. They didn't have to be good drawings or even make any sense, just angry scribbles on scrap paper or something. Art is expression, and expression doesn't have to be pretty; it doesn't have to be well done and it doesn't have to be a pleasant subject. Just as long as it doesn't make you feel worse. I know it sounds a little weird, and I can see how it wouldn't help everyone, but it allowed me to redirect those feelings and almost make them come out like they were trying to, but in a way that was safe for me. And art doesn't have to be drawing; it could be, I don't know...taking a cupcake and dropping an encyclopedia on top of it. I'm not sure what the meaning of that piece would be exactly, but as long as it had meaning to you, then it's art; and as long as it works to keep you safe, then it's worth it, because you're worth it, even when it doesn't feel that way.