You may have an anal fissure, which is a tiny crack of the skin within the anal sphincter,
I experienced the same sensation not long after takedown, the uncontrollable urge to push and bear down, although I also experienced excruciating pain during BMs, as well as the sensation of wanting to pass a golf ball sized object.
I applied ilex protectant paste to the inside of the anal sphincter; sounds rather unpleasant but it made all the difference.
Within a few hours of applying the ilex in such a manner and after every BM; the urge and sensation to push stopped and I was able to empty without straining.
Although, it does state on the box and tube, that ilex paste is for External Use Only.