Dog went crazy

Question
I have a female chihuahua who is about 2 1/2 years old.  She is typically a great dog.  We just got back from vacation and she was perfect while we were away.  We would take her outside to use the bathroom and she was just perfect.  
Now we are back home (where she was good before) and she has lost it.  We take her outside to use the bathroom and she will run off, which she never used to do.  Then last night I called her to sit with me on the bed while I watched tv and she peeeed all over me!  When I tried to tie her out she began flipping out and biting me.  She went crazy as if some one was trying to kill her.  I am wondering what to do.  Could this be hormonal.  I noticed when we were taking her for a walk that the other neighborhood dogs seemed to be barking more when we have been out lately, but maybe that is just me.  It has not been that long since she went in to heat I did not think it was that time again and she has not shown any signs of pregnancy. It would be very obvious by now. Thank you for you time!

Answer
Whenever one sees a behavior change as drastic as this, it is time for a thorough vet check to make sure that there is nothing wrong with the dog.

The running away and inappropriate urination can most likely be attributed to her being in season (although it might not be related), but the aggressiveness and biting is not. That almost sounds like a pain reaction, unless she has truly "slipped a cog" for some reason. Best to have her checked out, I think.

Karen