Any tooth paste is good for teeth provided if you do proper brushing twice daily. Do flossing daily. And for yellow teeth you should go for bleaching technique if you don't have sensitivity or for veneering treatment.
toothpaste r only cleaning agents n do not cure any dental probs. they help clean ur teeth. various brands differ only in colour n flavour. using proper brushing techniques with any toothpaste 'll b sufficient.
brush twice a day with soft toothbrush and fluoridated toothpaste. You can use any fluoridated toothpaste from any company, try and use one with soft bristles. It is not really the brush / paste that decides the cleaning efficiency, but the technique of brushing which ensures clean teeth and healthy gums.
teeth have a protective layer called enamel with age the enamel wears off and become thin which causes to become teeth sensitive to cold and hot. You need to get a professional check up done to know the exact cause and solution of your problem. Without checking you clinically we can't suggest anything.