I Had A Crown Done Last April And Root Canal

I had a crown done last April and root canal last june. There has been pain the whole time and major infection. the root canal was redone in October and crown replaced Dec 21 with all porcelain as i was tasting metal the whole time. The back of the first crown did not fit properly and the back of the tooth was exposed for months. I continue to have burning sensation to the area from tooth 46 to 48 around teeth gums and into jaw on right side. Any idea what is going on?