What could this possibly be?

I was not sure if I should ask this here or medicine. I figured this is more for animals.
My dog is not acting normal at all. I will take him to the vet tomarrow I just want to know what could be the problem.
symptoms
Bad breath- I gave him a dentabone and that did not help. Not the normal bad breath either almost like a sick breath.
nost hot and dry
the dog feels hot throught his body head neck limbs
not active- he is always full of energy
sleeping in the laundry room (away from people) which he NEVER does
will not eat much at all
limping on his front leg
I do not think his leg is broke I felt it and he does not pull away or wimper, it may be sprained or bitten by I guess a bug of some sort. It is swollen a little and warm.
Could he be like this because of a bite or is he sick? If he is If you can tell me what it may be I would bring it to the vet’s attention. If you know for sure that it is nothing serious and can get something over the counter or from the vet?
Another symptom is that he is shedding a lot. I know that it is a time of year but it is worse than ever before.

Any info on this I would greatly appreciate.
it. Sorry for my errors it has been a long night.