Ever since i suddenly developed a hydrocele, my penis has been shrinking a couple inches into my foreskin when i poop, and randomly at other times. why is this happening? is this an urgent matter?

A hydrocoele will generally not cause "penile shrinking", but increased abdominal contractions with for example, defecation efforts may cause retraction of the visible penis into the skin folds , making it appear as "shrinking" , but this is normal and not a concern or "urgent". If penile erection does not occur, see a urologist for an exam and guidance.

If the Hydrocele is large it can shift the penis slightly to the other side and make it appear smaller. The actual size of the penis doer not change. perception of size can. You will be fine and have the same size penis , don't worry.