Totally agree, had similar problem when woke up in pains in back so went to GP (the same day appointment) , she sent me to Urgences straight away where they inserted catheter and drained bladder - over 2 litres! Specialist then scheduled operation and prostate was reduced which resulted in 4 days in hospital. 2 things were / are a relief, firstly having the catheter out was heaven, secondly can now sleep without visiting the loo in the night.
Best of luck and hope all goes well.