Defecation, or feces, is a symbol for something that is wasteful in your life,....or something you feel the need to get rid of. That you can find no place private suggests you feel you have no privacy in your actual waking life. Feeling such urgency suggests that you feel pressured in your life. The anxiety you feel suggests you feel what you need to do within your waking life, won't be readily accepted by those in your social, and home environment. The feeling of shame suggests you feel guilty about something, as well as feeling bad about the decision you must make.
Because this is a recurring dream suggests this situation is bothering you greatly. And you're probably thinking something must be done very soon.

Is there someone, or something, in your life that you feel you'd be better off without?
Are you trying to break a longtime habit?
Do you worry about the repercussions your actions, or decision, will have?

Hope this helps you out, best wishes!