bald spots

My cat is a 2 year old Tortie named Trouble. She lives up to her name but I still love her. She recently, about a week ago, developed a bald spot on the base of her tail, and she has a straight line (about 2 inches) balding up her spine a bit from that area. She bites at the base of her tail which is making it bald, and my husband says it must be fleas. But, she has not been outside in over 3 weeks and we live in apartments with barely any grass. We have not been anywhere to bring them back to her, and neither of us have had any bites that we know of and she sleeps in bed with me. I've been putting hydrocortisone on it then distracting her so she won't immediately lick it off but I'm not sure if its helping. I rarely see her biting it but I also don't see her constantly. She only comes to me for sleep or play and does not like being pet very much. Anything I can do to narrow down what it could be?

Thanks,
Shyanne

I'ts possible that this could all be from one single flea bite, if she is allergic to them.  But it's strange if the bald spot is in a 2 inch line.  Is it a thin line?  Since it's along her spine, is it possible she is rubbing her back along something?  (really, I'm just grasping at straws here)  But you say she is biting at the base of her tail, and that's where the bald spot begins huh?  Is there any evidence of any little bumps or rash or anything?

I don't think I would continue with the Hydrocortizone cream, because I'm sure she is ingesting some of it, and that's not good.  I would at least call your Vet and ask them what they think.  They'll probably tell you to bring her him