Several spots on my lab mix

It could possibly be I would call my vet and just ask what he might suggest before it got any worse because could have got serveral different things or it could just be a reaction you wont know for sure unless you to talk to you vet.

It could be fleas or an allergic reaction. You could try to get medicated shampoo to see if that helps at all. Also a bath with added baking soda might help.

If it doesn't, I'd see a vet.

Take your dog to the vet immeditately! Any sign of pus is a sign of infection, and it is imperative that she receive vet care A.S.A.P.! From what you are saying about the bumps on her body, they have been spreading, and this could be something serious, or something benign, but from what you have said about your dog's behavior, she is clearly suffering. Do not second- guess, do not home remedy, get her to a vet. At very least, they will know if this is an allergic reaction to meds previously given, or something else- and as well prescribe an anti-biotic med or cream for the infection, and usually, they can give you something that will taste bad to the dog, discourage her from licking that area so it will heal.

The pus is probably indicative to an infection and needs to be treated. It probably became infected when she licked it raw and, like any open wound, became vulnerable to infection.
Ask your Vet to switch her meds. If that doesn't help with the bumps and the licking, try finding a dog food brand with out corn. Shepard mixes often have an allergic react to corn. This kind of dog food is similar in cost to other dog foods.

It is probably an infection (either bacterial, viral or fungal) or a reaction to something your pet ate or used. Either way, take your pet to check it out with the vet to be sure. If you do not get answers from the vet or if after seeing the vet, the condition does not go away... you may try a few home remedies that actually works for some dogs i've had in the past. Give your dog some probiotics - but specific type... www.florabalance.com ( use the powder to form paste and rub it on the bumps and infection area) and let your dog eat the powder off your hands or you may put it in your dog's water. It's own immune system will kick in, and your dog will start healing.

If your dog has been exposed to other dogs recently, it could be a community staph infection or at the worst, he may have contracted scabies (parasite) AKA mange. Go to the vet immediately!