I get so stressed when I need to urinate, to the point where I sometimes cry. How can I overcome this?

I'm not sure whether it's physical or psychological but I have a feeling it might be abit of both. When I need to urinate, I NEED to. I can't wait, I can't deliberate, I have to do it ASAP. It's not that I can't physically hold it, I could hold it all day, I just can't bare the sensation of needing the loo. It's so bad that if I need it really urgently but can't go it stresses me out greatly to the point of what I can only ume are mild panic attacks and sometimes crying. I can become extremely irrate and hard to talk to/think straight. At the moment I'm suffering cystitis which means I now have this feeling constantly, and I had a total breakdown on the train to work today - I couldn't handle being in public feeling this, even if it is a mild discomfort for most. How can I overcome this? It's really affecting my life.