I had absolutely no pain in my tooth. My dentist said something similar to yours, I had an old filling that had decayed further and he wanted to fill it. Well from day one, I experienced the same thing, extreme sensitivity to cold (which he said was normal). The pain never went away and got worse and worse. I did end up having to get a root canal, that got infected and I ended up having to get the tooth pulled. This tooth was towards the front and is very visible. I now have to get an implant. I regret having this filling done as the tooth never bothered me prior to this. Was this a white filling? I have done some research on white fillings after this happened to me and it is quite common for people to have issues with them. They do cause sensitivity and from what I have read it is not uncommon for people to need root canals after receiving these fillings. Good luck to you!