Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
However, seek urgent or emergency care if it occurs with new leg weakness, numbness around the genitals or buttocks, loss of bladder or bowel control, or an inability to pass urine.
These can be signs of a serious spinal or nerve problem.
Use local emergency or crisis services if you may act on those thoughts.
Seek prompt mental health support if distress about sexual function is causing severe depression or thoughts of self-harm.
Arrange a routine appointment if delayed or absent ejaculation persists, causes distress, affects a relationship, or makes conception difficult.
You should also seek assessment if the problem began suddenly, started after a new medicine or operation, or is accompanied by pain, blood in the semen, reduced sensation, urinary changes, low sexual desire, or erection problems.
The article also says
A sudden sexual change is not usually an emergency on its own.
Every sign above is quoted from the sofidex article on Delayed ejaculation. If you are not sure, err upward — it is always reasonable to be checked.