Boxer/Terrier with black spots

Question
Our dog is more than 75% Boxer and has several skin problems and allergies. Recently she started peeing more often, licking her paws and her butt (right at the base of the tail) more excessively than normal, and just tonight she exhibited black spots on her belly, and most all of her underside. They are not scabbed but appear fairly dry. We do not have the money right now to take her to the vet due to the holiday season. I am hoping that perhaps you may have a better understanding than we do as to what may be happening to our baby. Your time is much appreciated!

Answer
Licking the paws might be due to the allergies; licking the base of the tail might be allergies or impacted anal glands.  Frequent urination could be any number of things, depending on whether there's a discharge, increase in drinking, change in diet, etc.  The black spots could be dirt, a fungal infection, or simply pigment (you don't mention her age; pigment does continue to progress after birth, so sometimes black spots on the skin don't show up until the dog is older).  

It's very hard to give any advice without knowing a lot more about her history, diet, environment, etc.  There is a program called Care Credit that will help with financing veterinary expenses - http://www.carecredit.com/

Good luck!