Have just got a filling, mouth is still numb, why does it still hurt the same as before??

Depends...: After having a filling placed it is not unusual for the tooth to be a bit sensitive. However, if your tooth was causing you pain before, then you may have needed something different than a filling. Typically a cavity won't cause severe pain unless the nerve is involved. If the post-op discomfort is just sensitivity then give it some time. If you are having spontaneous pain, see your dentist asap.