Bad breath and bad taste in mouth.

I have chronic jaw pain. My tooth gum on second lower molar is painful. Went to dentist and took X-rays. He said it's normal. But gum was so painful when he probed and touched or rubbed those gums. I have bad breath in the mouth all the time. Even after brushing and using moth rinses. I feel bad taste and smell in the mouth. Do I have any infection in the mouth?  What does it mean to have bad breath and bad taste in the mouth ?. What should I need to do for the severe gum pain on this second molar? Its painful on the distal side of the tooth. And around the gum margin on that tooth. Tapping and pressing that tooth doesn't hurt. But touching and pressing the gum hurts. It hurts so much in the gum and throbbing like burning pain. I have yellow hard tartar buildup only on that molar and rest teeth are fine. That gum margin along with tartar buildup is hurting and painful on the gums. It's like throbbing and sore pain all the time. Do I need to ask for any  treatment on this tooth?