Sensitivity towards sweet food can be due to cavities
in your teeth
the sensation to cold
stuff also suggests that the nerve
inside your tooth
which is called the pulp is getting irritated because of cavities .even if you brush twice or thrice a day it won't matter unless you see a dentist
and get the oral examination done. After examination the dentist is going to evaluate the extent of caries and damage and suggest the treatment .this is the only solution for your problem which can be easily fixed once proper diagnosis and treatment is started.