Had wisdom teeth removed 5 days ago under general anaesthesia. Since then I have had the constant sensation of having to pee. How do I get rid of this?

Possible retention. After a general anesthesia some people will not have as efficient emptying of their bladder. This s usually short lived and 5 days would be uncommon for it to persist. Suggest seeing your family physician and obtain a UA and possible bladder scan as needed.