What is this on my dog ?

Hello Vets and Thank you in advance !  Several days ago , I notices 4 spots on my dogs stomach.  3 are very tiny , and the largest is the size of a nickel .  Originally it looked crusty, and I bought both a shampoo and spray that is both antibacterial and antifungal . Ive used it for two days , and when I used it , the crust dissolved and this is what the  spot looks like .    Does this look like ringworm to you ?  If he doesn't clear up in a few days after using the shampoo and spray I will take him to his Vet.  I don't know where he would have came into contact with anything . He is an indoor dog.  Only goes out to potty . Any thoughts are greatly appreciated . 

Hello!  The fact is that you can't always identify these things just by looking.  However you're right in that Ringworm, bacterial skin infection, allergy and even demodex mites, plus a few more obscure things, might make the differentials list.  Perhaps be careful where you put your fingers / be aware of anyone with low immunity or pregnancy in your household and continue to avoid other dogs, because if it were to be Ringworm, it is likely to be infectious.   Demodex and bacteria live on the skin all the time and multiply when the immune system takes a dive for some reason - stress, underlying pain, endocrine disease etc - or when the immune system goes slightly crazy ie in allergy.   Best of luck with it resolving and do let us know how you get on.