Dog bites herself until she bleeds and has giant bald spots?

I don't know what to do. She's either biting herself, or itching constantly and so roughly.  I've been on her *** about it lately but shes getting mischievous. She does it in general but she has some separation anxiety and every time both me and my boyfriend leave the room or the house she just starts going at it as hard and as fast as she can. We come back to her each time with a new bald spot on her butt and its super bloody from her biting it and there will be rubbed blood from her butt on the sheets. I'm almost threw with it and about to throw a cone on her darn head. Her fur smells a little odd where shes constantly itching or biting and its not a dirty smell either. We bathe her and use medicated shampoo and itching shampoo for her.  But it doesn't seem to be helping. She eats Iams food if that has anything to do with it, along with being constantly gassy. She has small red spotty bumps all under her arm pits and lower stomach and a little bit on the bottom of her paws. Any ideas?? :(

[Misfits4Me]

Hello, I'm not the Vet..She will answer before long.....In the meantime: Come over to the "Dog Forum", post your question and we will be able to help you out....