What are my throbbing gums a symptom of?

I have tooth sensitivity to sweet things… (which, incidentally I’d like to know why sweet things cause pain sensitivity more than hot and cold things for me….) and I have also been given a tooth night-guard for clenching my teeth… which doesn’t seem to help at all… but never mind… the dentist seems to think that it should be at least protecting my teeth from grinding (although I don’t do that anyway…I just clench…).

However, I am now experiencing more regularly prolonged throbbing and more acute sensitive deep pain after eating sweet things. The pain seems to go away after a while but the throbbing deep in my gum isn’t.

My dentist is as useful as a chocolate fire-guard and I am waiting to be transferred to a new one and I’m wondering if anyone has any advice on this matter?

Should I sack off the night-guard altogether as it seems to be causing me more discomfort than good and doesn’t seem to stop me clenching my jaw in my sleep as I’m still waking up with terrible headaches etc.?

Should I stop eating sweet things altogether?

Is the throbbing even a symptom of either sensitivity or clenching…?? Could the throbbing be something more sinister?
My teeth do seem to be very squashed on the side where the sensitive is mainly too… :-/