Pain after trimming of teeth

Hi, I had Last uppper tooth decay long back and I had filling as well. After 1.5 years, that filling came out. I could not do the re-filling for 3 months(there were no pain as well) and After 3 months I went to doctor and he advised to put crown and hence he did refilling without checking whether that went for RCT. He just refilled it with strong white composit. We gave gap for 3 days. There were no pain at all. After three days I again went to dentist and he did trimming (took out enamel). While doing it, there were lot of pain. He gave me appintment after 5 days for taking impression. Next two days I did not have pain but later on I had sever tooth pain and head ache. The pain was not only in that particular tooth but also near by teeth. Now I have a doubt whether the tooth gone for deep decay or the pain is causing due to mouth ulcer(which is there just behind that particual tooth and over the gums). This pain is not there all the time but only sometimes and at nights. Very sensitive for cold and any touch. Could you please advise what could be the problem?